Conference vmszoo::rc

    I get the feeling form this discussion that one adjust the pipe
    to fit a specific prop (size & pitch). Use an other prop & you to
    redo the tuning of get a new pipe..
    
    md

That is basically correct however if you tune the engine/pipe mildly it is less 
critical, as I said the Magic Muffler is a very broad tuned device, the ED pipe 
is a little more critical and the Pico is even more critical.

Tune the engine to your own requirements, if you want maximum power you have to 
be prepared to work on it, a little less power can be obtained with a more 
flexible power plant.

John.

re .-1
    
    pls define : "...flexible power plant"
    

re .-1
    
< pls define : "...flexible power plant"
    
A flexible power plant is one that is easy to use by the lesser experienced 
user. As an engine is tuned to its maximum performance you effectively narrow 
the operating environment. 

For example if we set up the clearances for a 60% nitro fuel low nitro fuel
will not run properly in that engine. As we tune towards a hot pipe we can 
no longer bolt on an of-the-shelf prop, we must then custom make props with the 
correct pitch and diameter. Too much pitch and we wont get on the pipe; too 
little and we will over rev and blow the engine.

Its all a compromise of flexibility and performance.

John

    re 65.2
    
    Do you happen to have info on what makes these pipes (magic muffler,
    Ed pipe & pico) behave so differently wrt to tuning ??

    re 65.5
    
    if one decides to use only off the shelf props, are you implying
    that one may not get full advantage of the pipe tuning.
    
    "get on the pipe" : please clarify..
    
    over rev engine: interesting observation since most manufacturers
    don't tell what is the rev limit one must not run beyond.. (now
    my car comes with a tach and a red-line indicator..). How do you
    decide when you are going to over rev ??

 
	re .-1

   
>    over rev engine: interesting observation since most manufacturers
>    don't tell what is the rev limit one must not run beyond.. (now
>    my car comes with a tach and a red-line indicator..). How do you
>    decide when you are going to over rev ??

              

		It goes BANG!!!!!



bob

		The difference is basically the length of the 
	pipe,measured from the inside edge of the exhaust port to 
	the end of the cone.the shorter the pipe the higher the
	revs it is tuned to..  can't remember the exact length 
	but on a .40 my ED pipe is around 20" long @12000 revs.
	Whereas a pipe on a .40 ducted fan engine which runs at 
	some 22000 revs is around 8-10" long.

			An engine is 'on the pipe' when the length
	of the pipe corresponds to the 'length' of the exhaust pulse.
	So the higher the revs the shorter the pipe,and the more 
	critical the length becomes..
	
                                   
	bob

    re .-1, -.2
    
    Sure they go bang !! 
    
    The tach on my car tells me what to watch out for. The owners manual
    tell about the consequences of running the engine beyond the red
    line.  Now, I get no indication what a the limits for my engine
    except that it has been run at 17000 rpm with a 8-4 prop. 
    
    You mention 22000 with a ducted fan and a pipe. 2-cycle engines
    can be revved pretty high. 25000 seems to be common without trying
    too hard. Now what is a generally recognized upper limit ? 27000,
    30000 ?? or "it depends" ???

< "get on the pipe" : please clarify..

If we have a engine Pipe combination set for 15,000-17,000 RPM the un-boosted
engine must be able to penetrate the 15,000 barrier in order to get the benefit
of the pipe boost. Sometimes we don't want the engine on the pipe on the ground
(eg. an aerobatic model during noise testing) so the set up is such that the
engine only gets on the pipe once the prop is able to unload in the air. 

<    over rev engine: interesting observation since most manufacturers
<    don't tell what is the rev limit one must not run beyond.. (now
<    my car comes with a tach and a red-line indicator..). How do you
<    decide when you are going to over rev ??

A standard engine run to manufacturers specifications will not over rev except
if you break a prop and get a shaft run. Once you modify engines anything can
and usually does happen. It depends on the engine and the modifications as to
what point the engine goes "BANG!". My Rosi 15 will quite happily turn 35,000
RPM as it is a bullet proof engine, however a standard OS40VRP Pylon engine
goes "BANG!" at about 25,000. Once we replace the rod, bearings, and backplate
with custom components we can run up to 35,000 but generally limit the top end
to 29,000. I have had the 40VRP up to 38,000 but the mortality rate was too
high, 3-5 runs only before the case cracked. We can use the pipe to limit the top
RPM. The pipe will stop boosting and prevent the engine going any faster, we
use this technique with the pylon racing models. 

< Re: Note 65.8

<		The difference is basically the length of the 
<	pipe,measured from the inside edge of the exhaust port to 
<	the end of the cone.the shorter the pipe the higher the
<	revs it is tuned to..  can't remember the exact length 
<	but on a .40 my ED pipe is around 20" long @12000 revs.
<	Whereas a pipe on a .40 ducted fan engine which runs at 
<	some 22000 revs is around 8-10" long.

Some people measure to the exhaust port, some to the center of the piston; it
does not matter as long as you measure on the center line of the header pipe
through the bends and always use the same technique. The only thing I will add
to the above is the angle of the cones affect the amount of boost, I think it
was the RCM&E magazine published a program in Basic for determining the
performance of a tuned pipe, I believe it was in the first half of 1985. If any
body has this program it would be good to enter in this notes file. 

The Magic Muffler is similar but not the same as tuned pipes. The MM has a
resonant mode as with the full length pipe but it also has an acoustic mode
that performs at lower RPM hence the wider power band. The MM was designed in
Australia by Ian McCaughey and Ranjit Phelan because of the need for a pipe that
fitted the old FAI F3D rules. Pappy DeBolt ran a series of articles on the MM
during the mid 70's. If you can find the issues they contain some good info. 

I hope that answers your queries without generating too many more questions.

John.

	re .9


		I wasn't implying that 22000 was any sort of limit,
	just an off the cuff example..

	
	re .10


		It may be in the feb 85 issue.I just happen to have
	the rest of 85s copies in the office,couldn't find it in
	those...



		bob

    re .10 : "generating too many more questions" 
    
    tsk tsk, john. Isn't this what notes are for: questions, question
    and yet more questions. I find the info you gave most interesting
    and educational too !!
    
    here an other: "Unoading the prop": pls clarify
    
    md

Sorry Marc you are correct, questions and answers is what a notes file is for.

< "Unoading the prop": pls clarify

A prop is loaded when it is in the stalled state.

When a model is stationary and the engine running the prop is in a stalled 
state as far as the lifting section is concerned; (the angle of attack is to 
great). As the model gains forward motion it effectively reduces the angle of 
attack and the prop now lifts rather than causing drag and turbulence; the 
prop is now unloaded.

There is one factor that confuses this very simplistic statement and that is
depending on the prop material and construction, the prop can actually be
feathering out due to the flexibility of the material used. For example if you
try to twist a nylon prop (nylon prop .. shudder!!) to change the pitch it is
much easier than say a glass reinforced prop. The greater the rigidity the
lesser the pitch variation during flight. 

The pitch variation is not all bad as it allows you to have a slightly reduced
pitch when flying uphill without the expense of a variable pitch prop, also it
allows you to carry more pitch than would normally be possible and still get on
the pipe on the ground. Maybe I can explain this phenomena with an example; I
made a prop for my FAI Pylon out of wood, tested and adjusted it for the
desired performance. I then used this prop as a mould for making carbon props
and found I had to carry about 1/8' less pitch. The overall performance was
much the same but the carbon prop had less tendency to change pitch day to day
and it was more resistant to chips and splits. 

Next question Marc.

John.

    Ah yes... an other variable into the pot..darn...
    
    what I read from this (.-1) is that once the plane is in the air,
    the engine is likely to get an increase in RPM (because of the lift
    effect) which would then allow (if you have a pipe connected) for
    the exhaust resonance to do its thing.. 

 the article in note 92 (schneurle porting) refers at one point to twin
    pipes and their turbocharging effect ..
            
    
    Cute !! . now can anyone shed some light on this one? Or do I get
    in touch with Mr Davis ??
    
    md

<    what I read from this (.-1) is that once the plane is in the air,
<    the engine is likely to get an increase in RPM (because of the lift
<    effect) which would then allow (if you have a pipe connected) for
<    the exhaust resonance to do its thing.. 

Not quite true!. It is not the lift of the prop that increases the RPM it is 
the loss of the turbulence and the associated drag.

John.

    re .-1
    if turbulence on ground with plane at rest affects RPM, what about
    mounting something (flywheel ??) that would load down the motor
    sufficiently to tune it properly ?? Is this realistic ?
    
    Or maybe build a mini wind tunnel ?? (One of those plastic barrels
    with both ends cut off fitted with a good fan could do the trick
    nicely) ...                          
    
    md

    re .-1

<    if turbulence on ground with plane at rest affects RPM, what about
<    mounting something (flywheel ??) that would load down the motor
<    sufficiently to tune it properly ?? Is this realistic ?
    
The problem with a flywheel is that it would provide little if any drag to the 
motor, also it would not give cooling to the engine or the pipe. The simplest 
solution is to have a prop you use just for setting things up on the ground. I 
use this technique for testing an engine on race day just prior to the first 
flight. The test prop is about 1/2" smaller in diameter than the running prop, 
it still provides some resistance and also keeps the engine and pipe cool. The 
RPM is known and provides a good comparison.

Sorry forgot to mention, as a pipe gets hot the tune point moves up. Very 
useful to get a bit of extra power in the air but a pain if the pipe overheats 
on the ground and the engine drop's of the pipe and quits. This mainly affects 
racing motors as other piped motors (eg. Aerobatic) do not run flat out for the 
duration of the engine run.

    I'v got a problem......My OS.25 won't put out!  I am noticing alot
    of fuel blowing out of the carb...I mean a good spray!
    
    At full throttle the thing barely lifts off the ground.  I've raised
    the gas tank to equal the carb (both in line) with no change.  I
    then lowered it, again, no change.
    
    The night before I dismantled the engine for cleaning, but it went
    back together fine.  So what could have gone wrong?
    
    I did get alittle pick up when I removed the low-idle adjust screw!
    
    Any ideas guys?
    
    
    LOST FOR IDEAS AND GROUNDED!

Fuel blowing out of the Carb is not uncommon on performance engines and does 
happen on normal sport engines to a lesser extent, I would not be too 
concerned.

I would check the following things:-

Stuck piston ring; make sure the ring is free and does not stick in the piston.

Has the liner been installed correctly; Exhaust port to the exhaust etc. make 
sure the piston is installed correctly, some pistons have a cutout that matches 
the transfer port to allow proper breathing, also the rod has a wrong way to be 
fitted. There is a small chamfer on one side of the Big End, this goes into 
the crank NOT AWAY from it. (common fault).

Is the Head aluminum shim in place, this can cause a problem with high 
compression and poor seal.

Also try different fuel, plug, and prop. I have seen a prop put on backwards I 
assume you did not do that.

If the incidence of the model on the ground is too nose down a model will be 
hard to lift off, it normally causes a leap into the air rather than a gentle 
lift off.

Try that to see if fixes the problem.

John.

    
    
    	If none of John's suggestion work send me the engine and I'll
    set it up on a test stand and see what can be done.
    
    	Q:  What prop size & Mfg. are you running?
    
    	Q:  What Fuel, nitro,Mfg?
    
    	Q:  What RPM's are you seeing?
    
    
    						Tom Tenerowicz
    						SPO Bld 104-1

    
    	One more thought, did you replace the back plate in the proper
    orientation. There is a flat on the inside of my .025FSR it has
    something to do with fuel/air flow, I'm not absolutely sure but
    it might be a problem. I know it can be put on wrong because I 
    did it and had to check with my shop to find the right way after
    doing some repairs.
    
    					Michael Gallant
    

    
        I'm pretty sure I put the backplate on the same way it came
    off, but now that you mention it, mine has a strange shape to it.
    It's not perfectly round.  Do you think that it would make that
    much difference in engine performance if it were in differently?
    
    As for re.21...
    
        I am using a 9x6 nylon prop Master Airscrew and a brand new
    batch of 10% BLAST.  I even went back to my old 12% BLAST but to
    no avail.
    
        I still think there is too much fuel blowing out the carb. 
    I have never seen that much come out before.
    
        Thanks for the input guys, any more ideas...please let me know.
    
    
    Ken

    
    RE .19 - May be a stupid question but I didn't notice any mention
    of the needle valve.  Does the engine simply not lean out when you
    screw the needle valve in (clockwise)???  To me it just sounds like
    you're running too rich, or maybe I'm missing something.
    
    								Bill
    

    I thought about that too, but the needle valve seems to function
    properly.  I did notice the engine pick up slightly when I pinched
    the fuel line ever so lightly (too much and it died).  I haven't
    double checked the backplate yet, but I think (due to identifying
    marks on backplate and engine) I put it on right.
    
    What a bummer.....I'm missing some nice flying time because of this.
    
    Ken

    If you are getting all the revs you are use to from the engine,
    I would recommend a change of propeller. Get one with a higher pitch.
    
    I had a similar problem with my FOX .19. It would rev up real good
    but the plane would have a devil of a time gettin of the ground.
    
    I was turning an 8/5. A 9/4 showed no noticeable difference.
    
    I wne back to my prop thrust table (remember the dicussion about
    props not being equal). I found that an 8/6 or a 9/5 would give
    me 30% & 60% more power for the same RPM. I couldn't find a 8/6
    so I settled for a 9/5. I got a drop in RPM (which I expected) but
    it was more than compensated by the increase in thrust. 
    
    The plane had ample power for take-off.  Flight performance was
    also substantially improved (I'm not sure I like that as I'm still
    trying to get my wings. My instructor loves the plane though).
    
    md 

    My problem is not enough RPMs!  The engine put out just fine before
    I took it apart.  I took it apart for cleaning because after  a few
    minutes in flight, the engine would start loosing power.  

    Check how you put the carburetor spraybar in.  I hear on some engines
    it is possible to put it in upside down (with the sprayhole facing
    into the incoming air rather than toward the crankcase).
     
    This not only screws up the mixture badly, but might explain why
    your engine sprays fuel out of the intake port.
    	
    	heck- it's worth a try.
    
    	-Bill
    

    SPRAYBAR!!!   You wouldn't be talking about the little bar connected
    to the throttle linkage would you?  I didn't think it mattered which
    way the hole faced.  Do you mean that one side is smaller than the
    other?  If so, I'll check it tonight!!   Thanks.

    
    	If you remove your idle adjustment screw(typically on the top
    right,viewed from the top rear of the engine) the throttle barrel
    of the carb should come out. Now remove the high speed needle
    and what you have left is a threaded tube with a fuel intake
    nipple on it. This is your entire spray bar. There should be one
    nut next to the nipple that locks this in place. loosen this nut
    and the spraybar will unscrew from the carb body. The spraybar 
    will have a hole on slot in it. Clear while you have it out.
    Now screw the spraybar back into the carb body and center the slot
    or hole in the center of the carb intake throat. Some OS carb
    spraybays are just a tube others have a slot or hole drilled in
    them at right angles to the tube portion of the spraybar. Whatever
    is the case you want this opening in the center of the throat. If
    it has a slot or hole drilled at right angles then you want to
    make sure that this opening points down the carb throat towards
    the crank case. When the spraybar is positioned snug down the
    lock nut and then  reassemble the remaining parts of the carb.
    
    
    
    					Tom

    
    I found the problem!   The info on the spraybar was helpful, but
    not the problem.  
    
    Two weeks ago when I disassembled my engine for a good cleaning,
    I accidently pulled the piston sleeve out of the engine.  When I
    put it back in, I aligned the exhaust port and figured all was 
    well.  What I failed to notice was there were two holes on the
    bottom of the sleeve that line up with two holes on the piston
    shaft!  I had the sleeve 180 out and that was causing the problem!
    
    I have since turned the sleeve around and the engine runs like a
    top!  Just something else to watch out for.
    
    Thanks for all the info guys.
    
    
    Ken

>    I have been having a similar fuel problem with my ST61 on a 
>    Cap 21.  I can adjust the mixture at full throttle with the main
>    needle, and at idle with the low speed needle, but it goes way
>    rich at anything in between with poor fuel consumption and lousy
>    throttle control as a result.  I end up flying at full throttle
>    because any throttle reduction causes a large drop in power.
>    Any help here would be appreciated.
    
>    Charlie

	* Charlie,  I don't claim to know a whole lot about Super Tigre carbs
	but I "do" know that there is quite an interaction between the high 
	and low speed needles which must be properly balanced to attain satis-
	factory mid-range performance.  The fact that your engine goes dead-
	rich at any setting between idle and full throttle suggests that the 
	low speed needle may be set too rich.

	How does the engine act when you advance the throttle for takeoff?  If
	it comes up slobbery rich, finally breaking into a 2-cycle, the idle
	(low-speed) needle is definitely too rich and needs to be leaned out.
	To determine where the idle adjustment is, let the engine idle for an
	extended period (30-seconds or more), then "slam" the throttle to full
	open and observe the engines reaction: if it slobbers in a rich 4-cycle,
	eventually picking up to a 2-cycle...or if it kinda' coughs, blubbers 
	and dies, the idle is too rich and needs to be leaned.  If, on the other
	hand, it instantly dies without a cough, splutter or anything...like you
	just flipped a switch to "off," it's too lean.

	I set my idle to where it goes through a short, momentary 4-cycle before
	breaking into the desired 2-cycle...this to assure the idle won't be too
	lean at the end of a flight when the tank is low on fuel.  Then, I set 
	the top-end for a click or two less than peak RPM and go back and re-
	check the idle.  If the idle requires readjustment, I do so, then re-set
	the top-end.  Just a couple of these cycles should dial in the correct 
	balance between the low and high speed needles and you should be able to
	pretty much forget the idle setting from now on, even when minor read-
	justments of the high speed needle are necessary.  If this doesn't re-
	solve the mid-range problem, you'll have to find someone with more moxy
	about S.T. carbs than I have.

	Hope this helps (let us know if it does)..., adios,	Al

    
    	Please try this.
    
    	1, Remove the pump.
    
    	2, Remove the carb from the engine.
    
    	3, Remove both the high speed and the low speed needle valves
    from the carb. 
    
    	   Now install the low speed needle valve into the carb. Look
    through the venture from the bottom of the carb and screw the lowspeed
    needle in until it is in the middle of the venture. Now install
    the highspeed all the way in. Reinstall the carb on the engine.
    Open the highspeed three tirns and start the engine. Adjust for
    high speed. Then go to idle and wait for app. 30 seconds. Now
    quickly go to high throttle. If the engine bogs then screw in the
    lowspeed ONE CLICK AR A TIME. Go to highspeed and adjust for MAX.
    RMP's. Go to idle for 30 seconds. Repeat this process until the
    low and high are set and the throttle responce gives you no sagging.
    
    
    						Tom

I have an OS .40 in my Eagle that is giving me fits. Maybe 
one of you RC gurus could give me some suggestions.

  o The engine tends to die at low speeds.  I noticed that 
    before it dies it starts smoking/spitting raw gas out of 
    the exhaust.
  o If I adjust it so it runs well at high speeds, it tends 
    to die at low speeds and vica versa.
  o The engine seems to start relativly easy when it is 
    cold but is quite harder to start when warm. (finger flip
    start method)
  o When trying to start the engine, I usually see bubbles 
    come up from the carb fuel intake into the fuel line.
  o If I block the carb air intake with my finger and flip 
    the engine over, I usually see a big air bubble enter the 
    fuel line from the carb and move back and forth, with each
    rotation of the engine.  When it starts this way, it will run 
    for quite a while while I keep the air intake blocked.
  o I, and others at the field with more experience than 
    myself, have tried to adjust the carb but just can't seem to 
    get it right.
  o I have checked the fuel lines and tank for leaks
  o I have disassembled the carb, cleaned out all orafaces 
    to no avail.
  o If I blow into the high pressure side of the fuel tank 
    with the carb fuel line disconnected fuel flows easily, 
    showing that the lines are not obstructed.

Any clues?

    
    Yesterday I noticed a number of planes with long tubs running off
    of their mufflers. Someone even noted that "it runs better" that
    way. I don't know what school of thought you guys are from but in
    my experience these tubes cause increased back pressure that robs
    am engine of power. Lets have a discussion about this. I'm interested
    in the opinions driving this and any hard data that may be out
    there. IE, RPM with tube,RPM without tube.. etc...
    
    
    Tom

    My sport-air 40 with an OS SF 40 was one of them. My first intention
    for this tube was to keep the glow glop off the alerons. The oil
    had a tendency to seep into the torque rods up into the wing and
    thus oil soak the balsa.  What I found was that the 1/2" x 24"
    tube actually increased top end power and made the exhaust a tad
    bit quieter. I have not got a tach, but I can feel a difference
    in the static thrust of the engine. Also the verticle performance
    is also much better with the tube on. Another thing that I found
    is that this engine likes to rev to make it's power. I get much
    better performance with a 10 x 5 prop than a 10 x 6 prop. Yes,
    it does appear to increase back pressure slightly if I remember
    correctly since when the tube is off the engine leans out ever
    so little. 
    
     When I have some time and equipment I intend to experiment and
    back it up with facts.
    
    
    
    						Dave
    

  I also have a tube on my exhaust.  The only reason I use it is to divert
the exhaust away from the plane.

  Jim

I think the tube acts like a mini-tuned pipe, since most of what
I've read mentions critical length, like 11 3/4 inches on the
Sportster .20.  I've tried to find some of the stuff, since I'd
also like to keep the "glo-glop" off my plane, but the local
hobby shops don't carry it.  What's everyone using?

    The clear plastic tubing that you find in hardware stores. The only
    problem is that near the muffler it gets rather warm and though
    the tube does not melt, it will conform rather nicely to any bends
    near the muffler outlet by kinking and thus narrowing the opening.
    I solved this problem with a small spring that I got from an old
    window shade. It had a nice 1/2" spring that was made of flat wound
    steel. I cut off about 2 inches of the spring and pulled on it till
    it expanded such that there was about 1/8 to 3/16 inch gap between
    each coil. I then stuffed this into the tube. I also fit the spring
    partially over the muffler outlet. I then clamped the whole
    assembly to the muffler with a small hose clamp. Works real nice.
    
    
    
    
    							Dave
    

There was a device called a  "Tuneable Tuned pipe some years back that simply 
consisted of a piece of stainless steel tube with a plunger that moved up the 
pipe to "Adjust the tune length". I tried one and could not measure any 
significant improvement in performance over a straight muffler. The engine I 
used was a OS 45FSR with raised exhaust timing so any boost would have been 
converted to extra power.

There is one possibility that can explain why the motor appears to give more
power as described in previous notes that is if the existing exhaust system has
some boost the lengthening of the tail pipe will pull the point where the boost
is detected to a lower RPM. On the minus side this lowering of the boost RPM
also reduces the maximum boost. 

This can be proven using a Dyno and plotting BHP against RPM. You will see the
broadening of the power band but flattening of peak power. 

In summery I don't believe the lengthening of the tail pipe will give more power 
just make more appropriate use; as far as the user is concerned, of available 
power from a particular engine/exhaust system combination.

I hope that makes sense, trying to explain without the use of drawings is 
difficult.

John 

    I have a K&B .45 that I'm just about ready to trash, unless someone can
    tell me what the problem is.
    
    The engine has about 50 flights on it, so I assume it's "broke in".  It
    starts very easy, and idles down to a very slow speed if I wish.  Also,
    the high end peaks out nicely, and has plenty of power. Nice snappy low
    speed to high speed throttle response with good mid-range control.  So
    what's wrong?  I can't get more than 5 or 8 minutes out of the engine
    in flight before it quits.  So,.. I dead stick in, and restart the
    thing, no problem.  I've tried richening the high speed mixture a bit
    before each re-try, but no luck.  During the last outing, I determined
    that the engine was overheating and seizing (yech). Didn't seem to
    wreck anything, since it goes back to "normal" after it cools.  I
    started doing more extensive bench tests to duplicate the problem on
    the ground.  Sure enough, I can get the thing to overheat just by
    running at full throttle for 5 minutes or so on the bench.  Something
    wierd is going on 'cause as it begins to get real hot (at full
    throttle) I richen the high speed mixture and it seems to have no
    affect.  The thing continues to get hotter and finally kills itself. No
    bubbles in the fuel line either! The mixture behaves just fine when
    it's cool. If it was the engine in a (real) car, I'd say it was a high
    temp vacuum leak leaning out the mixture.  I can't find anything wrong! 
    Could it be a leaky head, or some other obscure problem?  Other guys
    say that engine is junk, just trash it.  I don't want to give up yet,
    but I can't figure this one out.  I feel that both the high and low
    speed mixtures are plenty rich before the thing "flames out".  I can
    touch the head without burning myself at both high and low speeds. 
    BTW, I'm using 12% nitro fuel (never had any problems with it with my
    O.S. engines).   The engine is stock.  No funny modifications; same
    muffler, same carb.  I've tried cleaning the thing out a few times, but
    no luck.  
    
    Any ideas?  Anyone else with K&B trouble??   This engine runs wonderful
    before it overheats.
    
    thanks,
    ...bill

Bill

Sounds like an interesting one to me. Can you give some more information.

What is the condition of the plug after the run. Is it still shining bright or 
does it have a dull frosty appearance?. What sort is it?.

What size of prop are you using?.

What fuel are you using. you say 12%nitro, is it your own or a custom blend

Have you ever taken the engine apart?. could it be reassembled incorrectly?.

Is the engine in the open air or in a cowl?.

John

    
    What is the condition of the exterior of the cylinder?  Are the fins
    free of gunk or baked-on oil?  I had an engine that would overheat
    because of baked-on castor, which I solved by scrubbing and scraping
    (a real pain).  I hear oven cleaner works well but haven't tried it.
    I started using fuel with synthetic oil after that and have had no
    problems.
    
    When you say you are running rich, how rich?  Is it 4-stroking most of
    the time at full throttle?
    
    Bill

        Re:      <<< Note 65.40 by TALLIS::SAMARAS "Advanced Vax Engineering LTN" >>>

        Bill,
        
                I have the following suggestions:
        
                Make sure the engine has been completely run in.  The .45
        Sportster is an ABC engine and can have a very tight fit.
        
                Go up to  15%  nitro.    The higher the nitro content the
        cooler the engine will run. Not a lot of people know this!
        
                Make sure the tank isn't too low.
        
                With a full tank  the  engine should just break into full
        power with the nose raised  vertically.   If you lean it out with
        the nose level you are going  to  lean out too much at the end of
        the flight.
        
                      _ 
                     / |
        |  _====____/==|
        |-/____________|
        |    |        o \
             O           \ 
                          O
         Hang in there! o_|_
                          |
             Anker      \_|_/

>Sounds like an interesting one to me. Can you give some more information.

>What is the condition of the plug after the run. Is it still shining bright or 
>does it have a dull frosty appearance?. What sort is it?.

    The plug looked "normal" to me. It wasn't shiney, but it wasn't
    blackened. It seemed clean with no soot buildup. The idle bar was a bit
    dark.  The plug is an "RC short".  It has an idle bar.  The stock plug
    didn't.
    
>What size of prop are you using?.

    10-6  Doesn't seem to be over-revving. I guess it could be overloaded.
    
    
>What fuel are you using. you say 12%nitro, is it your own or a custom blend

    I'm using a "store_bought" 12% nitro blend.  It has some castor oil and
    some synthetic oil.  I don't have the breakdown handy.  I've used this
    stuff for a couple of years on O.S. engines without any problems.
    
>Have you ever taken the engine apart?. could it be reassembled incorrectly?.

    I did take the engine apart, but only after it seized twice.  I was
    careful to put it back together carefully.  It had the same behavior
    after re-assembly.  K&B enginges have an O-ring in the head. I think
    this could be a failure mechanism if it leaked.  It appeared to be in
    good shape.  I was careful to tourqe the head evenly.  The piston and
    sleeve are in in very good shape.  I thought they'd be scored.  The rod
    bearing on the crank was a bit tight though.  I cleaned the rod with
    fuel, and it loosened up fine. 
    
>Is the engine in the open air or in a cowl?.

    It's in open air with no obstructions.
    
    
    I played with the fuel tank pressure line.  I tried disconnecting it,
    and there didn't seem to be any difference (on the ground).  I never
    flew this way.
    
    
    Any help is greatly appreciated,
    
    ...bill

    Re .44
    
    I'm not an authority, but shouldn't that engine be using a long
    plug?  If it calls for a long and you use a short, I believe you'll
    get pre-ignition and overheating.  If its supposed to use a short
    plug, ignore my comments...

I can tell you whats wrong with it: the damn thing was made by
K&B!  We don't have a note for K&B woes here for nothing.  You
folks giving advice on this engine are making one big mistake:
you assume the engine is of the quality of say an OS and
therefore suffers from some problem -- not so, its a piece of
junk by birthright. 

This is the exact problem I've been having with my Sportster .20.
In the 2 years I've owned it I've never gotten a full flight out
of it. Sometimes the engine is so hot I can't even touch the top
of the carb to choke it for a restart.  And I run Cool-Power 5%
with a very rich mixture.

The engine seems to change its high speed mixture setting in
mid-run; I've tweaked it richer on the bench when it starts to
fade and have gotten ("have gotten" from a professional writer,
geez) a good run.  I can tell you that it is very, very sensitive
to mixture, and that the idle/high speed relationship is very
critical. 

After wrecking the old Qwik Stik deadsticking it in a few weeks
ago, I sent it back to K&B.  They returned it last week with a
new head, cylinder, and piston.  No explaination.  I suspect that
the little O-ring they use to seal the head/cylinder is a
marginal part and it leaks under heat.  If you get your mixture a
little off and over-heat it just once, the seal goes and you're
up the old creek with Dan.

This is a fine case in point on magazine bias.  To a man, all
articles on the .20 I've seen praise it.  Just this last issue of
MB, Stu Richmond had an article on an old-timer that uses a .20.
He joined the chorus of praises to the engine.  He reports that
he swings a 12-inch prop with it; I do not understand how he can
get away with it, given the engines tendency to overheat.

It is significant that the model had a very short nose length
(the distance between the CG of the wing and the backside of the
prop) -- the .20 is so heavy that a normal plane will almost
always need tail weight, assuming good construction techniques.
It is comparable to my Fox .36 in size and weight; contrasting to
my OS .25 that will bolt in interchangeably with a .15. 

    John,
    
    C'mon man!  Stop holding back; tell us what you _really_ think!  ;b^}  

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

Well, actually I have nothing but praises for the K&B -- I'd even
recommend one to my worst enemy.

    Since when does adding nito make a engine run cooler? An engine
    is basically a heat engine. Nitro has a much higher heat content
    and thus you get more power. If you run the engine at optimal peak
    needle setting, I have doubts that it will run cooler. 
    
    
    
    							Dave
    

    I'm afraid I have to agree with Dave.  The higher the nitro, the
    hotter the operating temperature.  Ask any pylon racer or power
    boater who runs 40% and higher nitro fuel.  How 'bout it John Chadd?
    You should be able to offer an expert opinion here.    

      |
      | |      00	 Adios,      Al
    |_|_|      ( >o
      |    Z__(O_\_	(The Desert Rat)

    thanks for the replys thus far...
    
    RE: .42
    I'm not running rich enough to cause "4-stroking"  Just rich enough to
    be off peak (making lots of smoke).
    
    RE: .43
    I did adjust the high speed mixture with the nose pointed up.  This did
    help, but it still goes into thermal run_away after a while anyhow.
    
    RE: .45
    I went to Tom's hobbies and looked at a new .45 to compare plugs. The
    factory plug was "about" the same length, but with no idle bar.  I have
    the factory plug, but it won't idle worth c%@p.
    
    RE: .46
    I think I'm becoming a believer that K&B is caca. Unless someone
    convinces me that I'm doing something wrong, It's time to by an O.S.
    I'm starting to believe that K&B's just ain't designed right. (???)
    
    
    THANKS FOR ALL OF THE IDEAS THUS FAR!
    -------------------------
    Anyone have a reliable .40 or .45 for sale for $50. or less?
    
    ...bill
    
    p.s. I still want to keep fiddlin' with the K&B, but I want to fly too.
    

    
>>    RE: .42
>>    I'm not running rich enough to cause "4-stroking"  Just rich enough to
>>    be off peak (making lots of smoke).
    
    Bill,
    I would suggest you try going richer.  Try adjusting the needle out
    until it 4-strokes, wait ten seconds and see if it leans out (also
    lift nose of plane).  If not go in a click and wait, etc, until it
    just starts 2-stroking.  I would not go any leaner than that.  I'd
    be interested to see if this prevents the overheating.  Good luck!
    
    Bill

Re: Note 65.42 by LEDS::LEWIS        

>    What is the condition of the exterior of the cylinder?  Are the fins
>    free of gunk or baked-on oil?  I had an engine that would overheat
>    because of baked-on castor, which I solved by scrubbing and scraping
>    (a real pain).  I hear oven cleaner works well but haven't tried it.
>    I started using fuel with synthetic oil after that and have had no
>    problems.
 
Oven cleaner will wreck an engine. Aluminium Fry Pan cleaner is ok and does a 
good job.

Re Note 65.45  By NYJOPS::BOBA 

>                            -< Right Plug Length? >-

The different plug length is supposed to allow for different head thickness. 
The change in compression caused by the different plug length can be use to 
give some adjustment of compression in performance engines, it will have some 
effect on sport engines but it should be minimal.


Re: Note 65.49 By TARKIN::HARTWELL 

>    Since when does adding nito make a engine run cooler? An engine
>    is basically a heat engine. Nitro has a much higher heat content
>    and thus you get more power. If you run the engine at optimal peak
>    needle setting, I have doubts that it will run cooler. 
    
Adding nitro can reduce the engine temperature as it increases the flow of fuel 
through an engine. Nitro is not in the fuel to make a big BANG!. Nitro releases 
oxygen and improves the combustion of the fuel (Methanol). Nitro is very hard 
to make burn that is one of the reasons you never see a fuel mix of 100% nitro. 

Your engine will run richer with Nitro fuels; the more nitro the richer needle 
can be set. The more fuel through the engine the greater the cooling effect for 
a particular power setting. Nitro is actually lowering the calorific value of 
the fuel, ie less heat. However; if this ability to burn more fuel is turned 
into extra performance up comes your heat generation (ie. F1 Pylon), so really 
Anker and Dave are both correct. (I should have been a diplomat)


>    The plug looked "normal" to me. It wasn't shiny, but it wasn't
>    blackened. It seemed clean with no soot buildup. The idle bar was a bit
>    dark.  The plug is an "RC short".  It has an idle bar.  The stock plug
>    didn't.

The plug will never be sooty. The plug is glowing at a bright red color so 
carbon will not build up. What does happen is that the plug goes frosty if the 
combustion is too hot. A good plug in a properly set up engine will always be a 
bright shiny appearance.

>    10-6  Doesn't seem to be over-revving. I guess it could be overloaded.
    
A 10 x 6 Master Airscrew or similar should be OK for a 40. It was said the 
engine was an ABC so any RPM up to 17,000 would be ok. I personally like to let 
an ABC engine have it's head and rev out particularly during the run in period. 
Provided you don't run it lean it should do no damage to the engine.
   
>    I did take the engine apart, but only after it seized twice.  I was
>    careful to put it back together carefully.  It had the same behaviour

I have seen an engine from the manufacturer assembled with the boost port over 
the exhaust. Make sure the exhaust port on the liner matches the exhaust on the 
case.

You also say the bottom end is tight. Check to see if the crank pin has blued 
from the heat. This is an indication that the bottom end is getting too hot. 
Also check that any lubrication holes in the big end are clear and the rod is 
fitted with the bevelled edge in the big end towards the crank shaft.
    
Another check. Remove the plug and wash the engine thoroughly in petrol (or is 
that gas?). Turn the engine over allowing the petrol to flow through the engine 
and remove all oil. I simply submerge the engine and turn it over for a minute 
or two. Now with everything dry and the plug still removed turn the engine over 
and see if it feels tight. It is quite normal with ABC engines to nip at TDC 
but you should still be able to turn it over using the prop backplate and it 
should feel smooth. If it doesn't you have to find out what is binding.

One final question. What does the engine feel like after it stops/seizes. Is it 
stiff through the entire rotation or just in particular places.

Try that 

John

    To start off if the engine won't run without an idlebar plug then
    the carb isn't set up correctly. Idlebar plugs were developed when
    carbs weren't able to be fine adjusted. Todays carbs really don't
    need idlebar plugs. The are used because then allow the average
    modeler a larger window of discression when fiddleing with the carb.
    
    Try the 15% fuel,try a rossi #6 or 7 plug. They run cooler.
    Take the engine out of the plane and run it on a stand and get it
    right. Then reinstall.
    
    
    Tom

RE: .53 (CHADD)
    
>A 10 x 6 Master Airscrew or similar should be OK for a 40. It was said the 
>engine was an ABC so any RPM up to 17,000 would be ok. I personally like to let 
>an ABC engine have it's head and rev out particularly during the run in period. 
>Provided you don't run it lean it should do no damage to the engine.
    
    I'm using a master airscrew 10 x 6.
-----------------
    
>I have seen an engine from the manufacturer assembled with the boost port over 
>the exhaust. Make sure the exhaust port on the liner matches the exhaust on the 
>case.

    I didn't think I could get the liner out of the cylinder.  I'll check
    it out this weekend. 
    
>You also say the bottom end is tight. Check to see if the crank pin has blued 
>from the heat. This is an indication that the bottom end is getting too hot. 
>Also check that any lubrication holes in the big end are clear and the rod is 
>fitted with the bevelled edge in the big end towards the crank shaft.
    
    I didn't take the crank apart, but it is blued a bit. I'll check the
    lube hole(s). The crank/rod bearing is tight. There is absolutely no
    detectable clearance. 
    

>One final question. What does the engine feel like after it stops/seizes. Is it 
>stiff through the entire rotation or just in particular places.

    Initially, by the time the plane was "dead_sticked" in, the engine
    cooled enough to appear to be completely free and normal.  However,
    during the most recent seizes, there is noticable stiffness through the
    entire rotation. When the cylinder was removed, I noticed how tight the
    rod was on the crank, and a bit of blue-ing as noted above.  As I
    mentioned back a few replies ago, I was amazed at how well the piston
    and sleeve looked (hardly any scoring... it was worse during break-in).
    So... maybe the rod bearing lube hole are clogged. Manually squirting
    fuel over the rod made it spin freely again.  Why would the bottom end
    get hot?
    
    BTW.. the plug element is bright and shiny like new.  The discoloration
    I talked about was on the idle bar.
    
    I'll be playing more with the engine this weekend.
    
    thanks,
    ...bill
    

                Nitro also  olwers the "octane" rating of the fuel, which
        means that higher  nitro  fuel  burns  faster,  that is the flame
        front moves faster in the cylinder.  If the flame front moves too
        slowly the fuel is still  unburnt when the exhaust port opens and
        the remaining energy in the fuel  becomes  pure  heat  instead of
        mechanical  energy.   An efficiently running engine  runs  cooler
        than an inefficient one.
        
                Byron's  sent  a  special bulletin out on the  Rossi  .90
        engine  warning  owners not to run it with less  than  20%  nitro
        because of overheating problems.  It was amazing how much  cooler
        the pipe became after I switched to the right fuel.
        
        Anker
        
        P.S.  After reading the last few notes I wouyld agree  that  your
        problem is a seizing big end bearing.

    
    
>> Oven cleaner will wreck an engine. Aluminium Fry Pan cleaner is ok and does a 
>> good job.
    
    Good point, I should have been more specific.  I thought I had
    heard of an oven cleaner made for aluminum but might have been
    thinking of what you mention.  The important thing is that you
    can damage an engine if you use the wrong stuff.  Thanks for
    clarifying that!
    
    Bill

    
    Great, glad to hear you found the problem!  The "stuck klunk" is fairly
    common after an abrupt stop of the plane - wonder why none of us
    thought to mention it???
    
    Bill

    I also had a problem this weekend with my old-reliable O.S. .25
    leaning out and being unreliable.  At first, I assumed it was the
    heat and humidity.  But, after a few flights, I noticed fuel was
    running out from the tank compartment.  

    I opened up the tank compartment and discovered a pinhole in the
    fuel line from the tank to the carb.  I had tried the "pinch off the
    carb line and blow into the pressure line" trick but the pin hole
    was small enough that the tank seemed to hold pressure.  There's no
    substitute for visual inspection...

    Apparently, air bubbles were getting in through the hole (thus too
    lean a mixture sometimes) and other times the fuel was squirting out
    into the tank compartment (probably while re-fueling).

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Caster Oil!! "    
                      |_____/

Ever seen pin holes in the pickup line inside the tank. Everything is fine
until you get below half a tank then it runs lean. 

Who ever check's an engine on 1/4 tank of fuel?. 

Unbushed rods are quite common and not as risky as you would think. Many
performance rods don't have them as the bushing actually weakens the big end.
The lack of a lube hole on the other hand is very uncommon in unbushed rods. 

You could safely drill a lube hole in the big end of about .015" dia. The
position is as looking from the rear of the engine at about 315 deg on the line
of the rod and in the center of the boss. 

The emery is a bit rough on the big end, a better way is a tapered reamer. If
the Crank pin has blued it is stuffed and you should replace the crank before
you fit a new rod. They never really work well again. 

Good luck 

John 

Engine = OS .45 FSR, mounted inverted.
This is the one I ran until the front bearing fell in so many
pieces that the chunks stopped the piston.
Bearing is replace now and there is some scoring but the
piston feels free in travel and smooth.

I thought I must have a pin hole or a leak in my clunk line on
my OS .45 FSR recently also.

It gave all the classic symptoms of an air leak.  Ran good
on the ground and you could hold the nose up forever.

Put it in the air and it would die.  Repeatable.

On further investigation - it did not run so well on the
ground.  Get used to using idle or wide open on the ground.
As soon as I attempted to run a tank thru at half throttle
it would die on the ground.

Every time it died - I assumed it was ceasing do to leaning
out.  So we were trying to run it sloppy rich.

I assumed that the reason the mid range would lean out was
cause the throttle was set too lean?

But I couldn't richen the throttle and have any idle cause
the engine is mounted inverted and would extinguish the
plug if I opened the idle adjust.

Sooooooo - I kept thinking that I must have an air leak
someplace.

Last night I took the fuselage into the back yard to troubleshoot.
I had a hard time getting it to run at mid range until I leaned it
out.

I ran one tank of fuel (8 oz) thru at sloppy rich.
Then I attempted to check the temperature with my Coverite pocket
thermometer.  I didn't trust the reading with the engine running cause
I figured that the air was cooling off the thermometer too much.
After the engine stops I measured the temp at approx 150 F but
again I don't trust the reading too much.  I ran it lean and shut it
down and the reading was about the same.  In all cases - running
rich or lean the engine is really HOT.

Anyway - I was determined to run a tank thru at mid throttle.
So I Ran a tank thru at full throttle and leaned out pretty good
and just backed off rich till I heard a change in RPM.  Ran great
but still very hot (burn your finger testing the muffler).

Anyway - then I ran a tank thru at half throttle.  I had to keep 
it lean cause it would load up and extinguish the glow plug
if it was at all rich.  In the end I got it to run at 1/2 throttle - 
but only if I didn't get it very rich.

Perhaps unrelated but what the heck.
It also makes some annoying shrieking sounds when it is running
at full throttle.  Not just two stroke sound and not prop noise.
Sounds kinda like  -  hmmmmm - shrieking.  But remember everything
turns nice and easy and the bearing FEELS good.

Sooooooooo - this brings up lots of questions.

1.  Is it normal to have to keep an inverted engine leaned out so
    as not to extinguish the glow plug.

2.  If I should be running a hotter glow plug - somebody please tell
    me how to buy a hot one.  What do I ask for?  Don't mind ordering
    special plugs from tower and spending a little more if it will
    allow me to run a tad richer and have more room for error in
    carb adjustment.

3.  What is a reliable way to determine if an engine is too hot?

4.  If an engine is too hot even when running sloppy rich and there
    is no resistance felt when you turn the crank shaft - then what
    do you do?

5.  Could it be that is is not getting lubricated as well being inverted?

6.  What do you suppose that shrieking sound is?  Scored cylinder walls
    breaking in?

    Kay, Often we don't see eye to eye or something. Guess this is one
    of those times... You've noted that you've spent nearly 1000.00
    dollars on your BJ's but still persist in trying to use a damaged
    engine. WHY??  I would think they deserve a good engine. At the
    contest the staticed good enough but clearly by your own admission
    the flight performance hurt you. BUY A NEW ENGINE. Stop putting
    yourself through this greif. If you buy a new OS45 you can use it
    in this present ship. You've noted that you don't want to because
    you plans are to ge into ships that won't be using this size engine.
    I think your fooling yourself if you think that you'll never build
    a .40 sized ship again. YOU WILL and when this happens you'll
    have a OS45 with limited use ready to be installed. Use the OS45
    you have today for parts or such...
    
    
    Tom

>    the flight performance hurt you. BUY A NEW ENGINE. Stop putting

If I had a spare $150 right now I would spend it on a Sniffler
for a glider.  In fact I just bought the Hobie Hawk from the for sale
add in this notes file for $150 tho it has been coming via UPS for
25 days now - sigh.

More to the point - I am not ready to give up on this OS 45 yet.
Granted I bought it used - but up until it ate a bearing it was
my most reliable and most user friendly engine.  If it is not economical
to repair I will replace it (probably with an OS 50).

I really don't mind fiddling a bit cause when that old .45 runs it
really runs.  Also I am not at all hesitant to do a dead stick landing
every flight if necessary and even during takeoff.  If I get myself
into a situation that can't be handled without power then shame on me.
I don't make slow inverted low passes (I can't).

Also don't forget I have two BJs.  If I crash one bad - well that's why
I built two.  I don't collect models.  I've never retired one.  I consume
them.  

At any rate - I am listening to your advice and depending on my success
with fiddling with the 45 I may buy a new engine.

About the $1,000.  You guys are missing the point.  It isn't that the
BJs are expensive.  All these planes are expensive - much more than
you would ever imagine unless you keep track.

Saying that I've already spent a lot therefore I should part with
another $150 to get a new engine makes me think that maybe you
are a Democrat running for Governor.  A hundred dollars still a lot
of money even tho it may be a small percentage of the whole pie.

Gads - I'm rambling again.

Any advice on the hot 45 questions?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    Kay,
    	It's normal for an engine to run hot on the ground, especially in
    hot, humit weather.  Also, it's normal to have more problems with plugs
    going out on a rich run with an inverted engine.  You're probably
    running it too rich possibly due to incorrect setting of the idle
    mixture screw.  To set that properly, first set the full throttle
    mixture with the needle to a rich 2-cycle.  Then go to idle and adjust
    the mixture until it will idle without loading up and slowing down and
    quitting.  Then try advancing the throttle fast.  If it's too rich at
    idle, it will take a couple of seconds to pick up revs.  If it's too
    lean, it will balk and die.  If it's just right, it should nicely pick
    up speed.  If you move the idle screw much, you have to go back and
    repeat these steps again since the screw will affect the high speed
    mixture somewhat.  Turning the idle screw on the 45FSR Clockwise leans
    the idle mixture.
    
    Hope this helps
    
    Charlie
    

>    	It's normal for an engine to run hot on the ground, especially in
>    hot, humit weather.  Also, it's normal to have more problems with plugs
>    going out on a rich run with an inverted engine.  You're probably
>    running it too rich possibly due to incorrect setting of the idle
>    mixture screw.  To set that properly, first set the full throttle
>    mixture with the needle to a rich 2-cycle.  Then go to idle and adjust
>    the mixture until it will idle without loading up and slowing down and
>    quitting.  Then try advancing the throttle fast.  If it's too rich at
>    idle, it will take a couple of seconds to pick up revs.  If it's too
>    lean, it will balk and die.  If it's just right, it should nicely pick
>    up speed.  If you move the idle screw much, you have to go back and
>    repeat these steps again since the screw will affect the high speed
>    mixture somewhat.  Turning the idle screw on the 45FSR Clockwise leans
>    the idle mixture.

Charlie - I think I have the idle right just like your description.  On
the .45 it is easy to adjust.  Inverted and too rich idle and it dies.
lean a little bit and I get a nice idle and can go to full throttle with
no hesitation at all.  

I think your 1st three lines describe my problem exactly.  It has been
hot and humid and the engine runs hot.  In the air I had been assuming
that it was leaning out but in reality now I think it was running cooler
and extinguishing the plug at mid throttle.

Just seems counter intuitive to keep leaning it.

Anxiously waiting the next test flight.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================
    

    Kay,
    
    What is the behavior if you run it wet and with the glow starter still
    on it??  Do you have enough room inside the BJ to put an on board
    ignition system??  This seems like the safest/least expensive thing
    to do.  A lot of people use them with inverted engines just to make
    sure they don't extinguish the plug...
    
    cheers,
    jeff
    

>    What is the behavior if you run it wet and with the glow starter still
>    on it??  

Runs great that way.

>    Do you have enough room inside the BJ to put an on board
>    ignition system??  

Room is no problem - in fact I need the nose weight.

>    This seems like the safest/least expensive thing to do.

Sure is cheap - in fact I have a gaggle of huge single cells from a 
bad DEC battery backup unit.

>    A lot of people use them with inverted engines just to make
>    sure they don't extinguish the plug...

Ahhhh - but do they run them continuously?  I've only seen them
installed where they kick on at low throttle.  I would need one
all the way up.

Also I am just uncomfortable with compensating for something that
should work.

Good idea Jeff - I hadn't thought about on board much - so if not
convinced by other notes I think I may pull out my lead weight
and install a battery and switch tonight - I have a heck of a time
getting the clip on my deeply recessed inverted engine anyhow - it
would be nice to just flip a switch for a change.    

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================

    

    The setups I have seen use a micro switch to turn on the system.  
    
    Mount the switch next to the throttle cable in the fuse.  Then,
    place a whell collar around the throttle cable and tighten it so
    that it depresses the switch at the correct point in the throttle
    throw.  If the arm on the micro switch is short, multiple wheel
    collars on the cable will insure that the switch is "on" through
    a wide throw.
    
    Good luck!
    jeff
    

>    The setups I have seen use a micro switch to turn on the system.  
>    
>    Mount the switch next to the throttle cable in the fuse.  Then,
...
Jeff - I know the setup - I've done it myself.  Problem is this needs
the battery on up thru 3/4 throttle and I almost never run at full throttle
except for take off and just a tad on some maneuvers.

Soooooo - will my battery and glow plugs last with it turned on thru
the entire flight (7 to 10 minutes)?

Bye          --+--
Kay R. Fisher  |
---------------O---------------
================================================================================
    

    Ah, yes, I missed the point of your that statement when I read it
    before...
    
    Yes, most people seem to use them just at the lower settings.  No,
    I don't know how well the batter would last.
    
    cheers,
    jeff
    

    kay,
    
    understand that i'm rooting for you and want you to succeed.  like
    many others i vote you buy a new engine.  if not, debug the os45
    methodically.
    
    remove engine from plane and install on test stand.  install brand
    new or known good tank and fuel line.  eliminate variables.  in
    fact, start with one variable, the engine.
    mount upright, use stock muffler and exhaust pressure.  use known
    good fuel.  you better be able to get the engine to run flawlessly
    in this configuration.  otherwise junk engine.
    
    so it runs great upright.  try inverted.  it should still run great.
    does tank position affect it?  maybe, just maybe an on-board ignition
    setup is needed for reliable idle, but not midrange.  that should
    be flawless.  if you havent thrown engine in dump yet, try original
    tank.  then ...
    
    the point is to remove all variables and start debug methodically.
    its got to be easier than fiddling at field on your knees in hot
    sun.  there may be a combination of problems, maybe some intermittent,
    that could make debug time using your current shotgun approach
    infinite!
    
    when making needle adjustments, make adjustments in increments of
    clicks or 1/16 of turns, not 1/4's of turns.

    do you know why your carb leaks fuel when sitting on ground with
    tank filled?
        
    it could be anything.  i dont trust your tank, fuel lines, kwik-filler,
    tank position, glo-plug, cowling, needle valves/adjustments, bearing,
    carb, fuel, engine, engine, or engine.
    
    i fear that someday that unreliable engine is going to cost you
    a very nice airplane.
    
    good luck
    kevin

    Has anyone with a Supertiger engine used one of Higley's replacement
    needle valves??
    
    As I mentioned in "the Wreckord" I broke the needle valve of my ST 40
    off last week.  ST parts are hard to come by around here (Southern NH)
    so I bought a package of "Little Tiger Needle Valve".  These are the
    shorter stemed needle.  
    
    The symptom that this is the wrong one is that the needle has *no*
    (none, nada, zippo) effect on the high end...  It can be cranked down
    to 0 turns or open to 5 and the engine runs the same.
    
    So, my question is, is there a difference between this needle and 
    Higley's other ST replacement valve??  (according to the Towers
    catalog, one size fits all??)
    
    If there isn't a difference, what am I doing wrong??
    
    thanks,
    jeff
    

    Re: .-1, Jeff,
    
    I have no personal experience with or knowledge of the performance of
    Higley's after-market needle valve...fact is, I didn't even know he
    made one 'til now.  However, if you are experiencing problems that
    didn't exist before using the Higley needle, you can bet the ranch that
    it's the culprit!  Heck, I've even experienced problems using an
    identical (supposedly), factory replacement part.  Save yer'self some
    grief and order several replacements from the manufacturer/distributor.
    I'm all for after-market products but sometimes they simply fail to do
    the job.
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

    I have a Super Tigre 61 that's working just fine with all original
    equipment (so far). I have noticed that needle valve adjustments
    are VERY sensitive. Setting up the low end is done one click at
    a time. Given this sensitivity, any replacement needle that
    isn't dead on spec's will no doubt give you problems.
    
    Where the plane was involved in a crash, there is one other possibility
    for the symptoms you describe. Make sure your getting tank pressure.
    I say this because I bought a Pitts muffler for mine and the engine
    exhibited the same symptoms. Turned out I had to completely block
    off one exhaust tube and restrict the other in order to get enough
    fuel tank pressure to get a reaction out of the needle valve. In
    fact, the engine never did run that great with that muffler, so
    I'm back to the original.
    
    Steve                          

    Is back-pressure "essential" to a smooth running engine?  My brother
    has a ???? engine, (alot like a Supertiger), but doesn't have a 
    muffler.  It is extremly hard to adjust the high end.  Any comments?
    
    Ken

    Well, I have PROVEN that ST engines are not idiot proof.....
    
    I went to Bill's Hobby Barn at lunch today, with my needle valves in
    hand.  I then compared the ones that I had bought with the "extra long"
    version.  Sure enough, not only is the shaft longer, but the needle
    and the thread are both longer as well.  So, I bought the wrong
    replacement. 
    
    ST, apparently in a move to standardize, apparently uses the identical 
    thread and diameter, just different lengths...  Thus, you can buy
    the wrong one, which apparently fits, but will never work.  Ug!
    
    So, I believe I will have much better luck this afternoon....
    
    Thanks!
    jeff
    

    Re: .-2, Ken,
    
    While it's become almost universal in practice, muffler pressure should
    not be essential to an engine running satisfactorily, especially at the
    top end.  Where muffler pressure is a real boon is at low speeds where
    crankcase vacuum can be marginal in terms of providing adequate fuel
    draw; a little pressure in the tank assures a positive fuel flow even
    though crankcase draw is minimal.  This is especially true if the tank
    is located lower or farther behind the engine than is desireable. 
    However, performance should be little affected at high rpm where draw
    is at max, unless the tank position is _really_ marginal, in which case
    muffler pressure may not be adequate to compensate anyway.
    
    Speaking only to 2-stroke engines, if the tank is located as close as
    possible to the engine with the feed line level with (or just _slightly_
    lower than) the needle valve, it should run just fine.  We ran 'em this
    way for years with no problems of any particular consequence.  In this
    situation, muffler pressure enhances idle dependability but, again, has
    little noticeable effect on high rpm's.
    
    I, personally, wouldn't even consider running an engine without muffler
    pressure but you shouldn't expect it to be a panacea for everything that 
    ails it.  As often as not, most problems with 2-cy engines can be traced to
    one or more of the following: poor carb and/or needle adjustment; poor
    or faulty tank installation and/or bad fuel system integrity, i.e.
    leaks, pinholes, etc.; bad/old fuel or bad glo-plug.  
    
    The one thing that should be mentioned also is that model engines can all 
    too easily be permanently damaged by poor operating techniques; if not
    treated correctly and with respect for this fact from the beginning,
    that expensive mill can readily be converted into a paperweight.  Once
    so damaged, no amount of fiddling or ancillary gadgetry can fix 'em.  Send 
    'em back to the factory/distributor with a complete/detailed description of
    the sysmptoms, including such vitals as fuel, prop and plug used and
    they _may_ be able to restore the mill.  Be honest and include even
    'dumb' things you might'a done...if they don't have the _whole_ story
    to work from, even the factory/distributor could easily miss the
    problem.
    
    I don't mean to insinuate that these mills are fragile or delicate.  On
    the contrary, they're quite rugged and will tolerate quite a bit of
    mishandling...but _just_ so much!  I encourage all newcomers to read, 
    read and re-read the manufacturer's instructions and do everything 
    possible to follow the recommendations therein.  This should prevent you 
    from inadvertantly harming yer' precious little powerplant but, if you take
    it out'a the box, do a slipshod job of installing it and the fuel
    system, then ignore the mfgr.'s operating recommendations, yer' almost
    doomed to ruin the engine and have a lifetime of grief with it.  If
    you're still a confused rookie, engine-wise, don't simply grope yer'
    way blindly onward, G E T  H E L P!!  Just as in flying itself,
    obtaining experienced/expert help early on can and will prevent a
    multitude of grief later on!!
						 __
	 			|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

Now that Al has put his two cents worth in (penny a note is a good price ;^)

I had a similar problem for different reasons. I had been out of it for several 
years and my flowthrough muffler didn't meet today's specs. I couldn't find a 
manufacturer's muffler for my 18 year old Webra so I bought a (great in my
opinion) SoundMaster muffler. The problem I got into was that my Perry 
replacement carburator couldn't meter the fuel with the extra muffler pressure so
I had to go back to the original carburator which had been too sensitive without 
the pressure (years back).

Muffler pressure can complicate things but it does give you a broader range of 
reliable throttle settings and there are several good/great 3rd party "universal" 
mufflers for those out of production engines.

My problem now is getting parts for my old engine since the US distributor has 
changed.

    Re: 65.87
    
    Jim,
    
    let me know what WEBRA parts you need. Maybe I can dig them up here in
    Germany (where WEBRA is at home and you find many of their engines). I
    would then try to talk Bill Lewis into taking them to you when he
    leaves KBO in about two weeks.
    
    Regards,
             Hartmut

    Thanks Al,
    	
    	I was really hoping you would say the muffler would make all the 
    difference.  This carb has THREE adjustments instead of the normal two
    that I am used too and believe me trying to adjust it without any
    instructions is tough to do!
    	We tried changing the plug, and the fuel was new, so delete those
    two from the list of things to check.  I think it is just a matter of
    getting all three settings properly set....but what is properly set?
    
    Ken

    Last night, I had an interesting problem with someone else's engine. 
    After over an hour of fiddling, we finally found the problem, but
    instead of just telling you, I'll pose it as a "stumper" question;
    aimed at John Chadd in particular, but everyone, please feel free to
    take guesses at the problem.  

    Background:  The engine is on a new trainer and has only 4-5
    tankfulls run through it so far.  (OS .40 or .46 SF, I think)  Has
    been flying OK (still set rich) but dies occasionally in the air. 
    While on the ground we're trying to get the mixture set better so it
    won't die in the air.  As we're messing with the engine, it
    degenerates into the following problem:

    Problem:  When the engine is running with the plug warmer on,
    everything seems OK, but as soon as the plug warmer is removed at
    any throttle setting, the engine quickly dies (even at FULL throttle).

        Tried a new plug.  No difference.
        Tried flushing out the carb.  No difference.
        The fuel lines were not pinched and did not have any pinholes.
        Tried some fresh fuel (known to be good).  No difference.
        Tank height is OK.
        Plug warmer battery and connections are OK.

    After all of these attempts, the problem is getting worse and worse
    until it won't run at all.  When the starter motor is applied, it
    runs for 1-2 seconds, sounding very rich, then it speeds up like
    it's too lean and dies quickly.  Does the same thing even with the
    plug warmer still on.  (Frustration level is now at a maximum...)

    Finally, won't even run for 1-2 seconds even though the plug warmer
    battery is still in good shape and is left connected.  Turning the
    needle valve in or out makes no difference.  Engine is "popping" a
    little when starter motor is applied, but won't run on its own.

    >>>>>>>>>    What is the problem with this engine????    <<<<<<<<<

    (If no-one gets it in 1-2 days, I'll post the answer...)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    >>>>>>>>>    What is the problem with this engine????    <<<<<<<<<

My guess.
Glow plug (cracked or broken) or head loose.
Same symptoms - no compression and getting worse.

Bye          --+--
Kay R. Fisher  |
---------------O---------------
################################################################################

    I agree with Kay. I had a similar when I lost a crankcase backplate
    screw and developed a crankcase pressure leak. It couldn't get fuel
    onto the piston. This was made worse by the exhaust priming method we
    were using since it would burn off the prime and quit.

    RE: .91 & .92  

    Nope - the compression was fine.  This was not the problem.  All
    bolts were tight.  (We checked.)  Changing plugs had no effect.

    A small hint is that we were (finally) able to resolve the problem
    at the field and get the engine to run fine.  (But still
    intentionally running a little on the rich side since it's so new of
    an engine.)

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    Muffler pressure line had become disconnected? You only mention fuel
    lines being good.
    
    ajai

    Nope.  All fuel/pressure lines were correctly connected and in 
    good shape.  (No pinholes or cuts in any of the lines.)

    Keep guessin'...

I love a challenge unfortunately the manufacturers of model engines have not
developed RD tools to the standard we expect from DEC. I will give it a go. 

>    Problem:  When the engine is running with the plug warmer on,
>    everything seems OK, but as soon as the plug warmer is removed at
>    any throttle setting, the engine quickly dies (even at FULL throttle).

Normally a symptom of a too cold plug on not enough compression. From later 
notes I assume this was not the problem.

>    Finally, won't even run for 1-2 seconds even though the plug warmer
>    battery is still in good shape and is left connected.  Turning the
>    needle valve in or out makes no difference.  Engine is "popping" a
>    little when starter motor is applied, but won't run on its own.

Again I concur it sounds like a bad pressure line. 

Hm! What next. I would check the needle operation and engine compression; you 
say however it was not the problem and you fixed it on the field. Think. Think. 

I had a similar problem with a cracked crank case but that's not something you 
fix on the field. Did you say that the crank case pressure was ok? could you 
draw fuel through the engine?

Well my guess would be something causing fuel restriction (ie: Heating the fuel 
line or loss of crank case pressure, possibly a problem with the carb operation 
such as a bad seal or ineffective barrel.

Go on Dan give us the answer it has me intrigued.

John

RE: Note 65.96 by SPREC::CHADD

>I had a similar problem with a cracked crank case but that's not something you 
>fix on the field. Did you say that the crank case pressure was ok? could you 
>draw fuel through the engine?
>
>Well my guess would be something causing fuel restriction (ie: Heating the
>fuel line or loss of crank case pressure, possibly a problem with the carb
>operation such as a bad seal or ineffective barrel.

    Oh boy!  I stumped the engine expert!!!  Hurray!!!  First of all,
    I'm sure John would have gotten this if he were at the field, but it
    sure had us stumped.  (For more than an hour...)

    The problem was:


    The muffler was 1/4 to 1/2 full of fuel!!!  The adjustable muffler
    exit hole was pointed up instead of down and all of the rich running
    we had given it allowed the sloppy exhaust to build up in such a
    fashion as to become quite a problem when running the engine.

    We had all given up (it was getting dark) and the owner
    dis-assembled the plane and began cleaning it up.  As he picked up
    the fuselage by the spinner, he tipped it up and I noticed a LOT of
    fuel/oily glop run out of the muffler.  

    I yelled "THAT'S IT!!" so loud that he darned near dropped the plane.  :-)

    After we tipped the plane so that ALL of the goop drained from the
    muffler, and re-adjusted the needle valve, the engine ran just fine. 
    (Considering that it is not borken in yet and required a rich
    setting.)

    The muffler exhaust exit hole now points DOWN instead of UP!!!

    The best I can think of is that the excess fuel was DROWNING the
    plug on the intake stroke.  With the glow plug warmer connected,
    there was still enough heat to keep it running.  (Until there was so
    much fuel in the muffler that even that couldn't keep up with the
    sloshing...)  To make matters worse, the muffler/cylinder connection
    is on the bottom of the muffler:


   |------------------|                    --------
   |                  |                   /        \
   |                  |                  /          \
   |                  |                 | Muffler    |
   |                  |                 |  (rear     |
   |    Cylinder      |                 |    view)   |
   |                  |                 \           /
   |                  |                  \         /
   |                  |                   \       /
   |                  +--------------------       |
   |                                              |
   |                  +---------------------------|
   |                  |


    Has anyone ever HEARD of such a thing????   None of us had...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

I don't doubt you Dan but it is the last thing I would suspect. Normally the 
gasses will blow any build up out of the exhaust. 

Good find.

John

    That's what we thought at first too.  But, ya' can't argue with the
    evidence.  :-)  Maybe I'll try an experiment with my trusty,
    reliable OS .25 FP sometime and intentionally fill the muffler with
    extra fuel and see if the symptoms can be reproduced...

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    Be careful not to hydrolock the engine and then bend the
    crank/connecting rod with the starter.

    I don't read RC much any more, so I'm a month late seeing this.  The
    problem with the new SF engines is the baffle in the muffler.  I've
    seen this problem on two 46SF engines.  The baffle keeps the exhaust
    from blowing the oil residue out unless the muffler is at an attitude
    where the outlet is low enough.  The problem usually happens with
    upright engine setups because the muffler is not below the exhaust
    port.
    
    Charlie