Conference vmszoo::rc

    
>    Which reminds me of yet another
>    question. Saito 45, OS 48 Surpass, or OS 61????????
        

    Dan, for a .40-sized trainer the Enya .46-4C 4-stroke would be a
    good choice.  It is definitely more rugged (and powerful) than
    the old OS .40 4-stroke, but I don't know about the new surpass
    engines.  OS may have caught up to Enya with the surpass
    but from experience with the Enya .46-4C I can definitely recommend
    it.  I used it in my Citabria (69 in. wing span, about 5 lbs) -
    the plans called for a .40 sized 2-stroke.  With an 11X7 prop it was
    actually overpowered.  I had trouble getting it to idle well 
    because the engine was mounted inverted.  I ended up using an on-board
    plug warmer that kicked in at idle.  Right side up or side-mounted
    they idle great.  Whatever 4-stroke you choose, be prepared for
    a lot of tinkering until you get used to it.  They definitely are
    not as easy to use and maintain as 2-strokers.  But you'll be very
    happy with the reduced fuel consumption and CLEANLINESS - no oil
    sprayed all over your plane!  By the way, Red Max 10% 4-stroke fuel
    worked good for me.
    
    Bill

        Re:< Note 411.0 by SVCRUS::EVERS >

                I have  three  four strokes.  An O.S.  FS 20, an O.S.  FS
        40 Surpass and  a  Saito  45.    I'm very happy with all three os
        them.  The guy  who started messing with the valve gaps must have
        had 10 thumbs.  First  of  all  they don't need adjustment except
        once in a blue moon, secondly  it's  a  five  minute job with the
        tools that come with the engine.
        
                The advantage with four strokes if the  low and realistic
        sound, the low fuel consumption and the high  torque.    I prefer
        four strokes in spite of having several other engines.
        
                I personally don't believe four strokes are any harder to
        deal with than any other engine.  I see the sam proportion of two
        stroke  owners  as  four  stroke  owners  struggling  with  their
        engines.  As  a  matter  of  fact, the engine problems seem to be
        more related to the operator than engine type and make.
        
        Anker

    
        Another question I have is I'm running 10% mixture for
      my O.S. 40 2 stroke and still have 2 gallons left can I
      use the same mixture for the 4 strokes?If not what is the 
      mixture for the 4 strokes?Also is there a break in time
      for the 4 strokes like the 2 strokes I broke my 2 stroke
      in by running it rich for 2 tanks.
        The reason I'm asking these questions is because I've
      never played with these four strokes.
    
                                          KEEP'EM FLYING
                                          JERRY
    

        Re:< Note 411.2 by SVCRUS::EVERS >

                I initially  used 4 stroke fuel but switched to 2 stroke.
        2 stroke fuel  has  a  higher  lubricant  content  and  therefore
        protects your engine better,  the  only  drawback is that you may
        emit a bit more oil  fumes  than  you  necessarily have to.  Well
        worth the insurance.
        
        Anker

    Jerry,
    
    I'm sure I'll be corrected if I'm passing bad info here, but I believe
    the primary difference between 2-cycle and 4-cycle fuel is that
    4-cycle fuel contains a lower percentage of oil.  The rationale
    behind this escapes me to some extent; on the one hand, the 4-stroke
    engine runs slower than a 2-stroke and has only half the firing
    strokes of a 2-stroke for a given RPM but, on the other hand, I'm
    given to understand that 4-strokes run hotter than 2-strokes.
    
    At any rate, if my originally stated premise [less oil in 4-stroke
    fuel] is correct, it'd be safe to run 2-stroke fuel in a 4-stroke
    engine [with some degree of diminished performance] but the reverse
    would "not" be true.
    
    Adios,	Al

Al is absolutely correct the only difference between 4st and 2st fuel is the
oil content. It is true that 2st fuel will work in 4st motors but it is more
difficult to get a reliable run as the excessive oil tends to put out the plug.
I would never use more than 15% oil and on the smaller 4st it is safe to go
considerably less, I would stick in the 10-15% range for safety. Some nitro
(5-10%) is preferred again to improve the idle. 

Have a look at the note on fuel in this conference, it gets into more
discussion on oil's etc. 

John 

    
    I have an Enya .46 4-stroke, and have seen several OS .40 4-strokes.
    I must disagree with Anker about the reliability between 2-strokes
    and 4-strokes.  My personal experience is that 4-strokes require
    much more attention (but that doesn't mean I don't recommend them).
    
    When the Enya .46-4C came out it blew away the OS FS40.  The Surpass
    line is OS's answer to that, and it looks like a good engine, but
    I don't have any experience with it.
    
    The most common problem with 4-strokers is with the valves.  Mine
    has steel valves with a brass seat, and the brass seat takes all
    the abuse.  I had to reseat the valves after one year because most
    of the compression was gone.  I used very fine grit lapping compound
    and this brought the compression right back.  One of the dangers of
    using too much oil, I believe, is that the valves can get gummed up
    and start closing late.  When this happens the valve seats get abused.

    I initially used 2-stroke fuel with the Enya but after the valve
    problem I switched to Red Max 10% nitro 4-stroke fuel.  Haven't
    had a problem since.
    
    The thing I love most about it is after a day of flying, you pick
    up the plane and wipe a small streak of oil off the bottom of the
    fuse, and your cleaning is done!  The sound of a 4-stroker is much
    more pleasing too.
    
    I forgot to say that I would not recommend trying to mount one inverted.
    I had lots of trouble getting mine to idle inverted, and finally had
    to install an on-board ignition.  It always idled beautifully upright
    though.
    
    Just my observations,
    
    Bill

        G'day

>    I forgot to say that I would not recommend trying to mount one inverted.
>    I had lots of trouble getting mine to idle inverted, and finally had
>    to install an on-board ignition.  It always idled beautifully upright
>    though.
    

	My OS 40FS is mounted inverted, and idles just fine... Sometimes
	it's a bit of a pain to start tho'..... I normally use 5% 2 stroke
	fuel...  

	I go along with 4 strokes being no more problem than 2 strokes.
	

	cheers

	bob

    One difference between 2 strokes and 4 strokes is the extra importance
    of rust and corrosion protection.  Some unburned fuel gets blown
    by the piston and ends up in the bottom end of the 4 strokes.  This
    is how the bottom end gets oiled.  Unburned nitro is corrosive as
    hell as is methanol in the presence of moisture.  You must get plenty
    of after run oil into the bottom end bearings after using a 4 stroke.
    I have seem many flyers get almost no use out of a new 4 stroke
    because they failed to oil it up after use.  When you run a 4 stroke
    out of fuel, you do not purge the bottom end of unburned fuel as
    you do with a 2 stroke.  Another difference between 2 strokes and
    4 strokes is the fact that 4 strokes burn much of the oil during
    combustion.  The exhaust temperature is much higher than a 2 stroke.
    You can char balsa if you run the exhaust pipe too near it.  If
    the burning oil creates carbon, you will carbon up the valves and
    have compression problems.  The best thing to do in the fuel department
    is use what is working for the people who are having good luck with
    4 stroke motors at your flying field.  Don't try to save a few bucks
    and use old fuel or the wrong fuel.  You will be sorry you did if
    this causes you any grief with your engine.  I have learned the
    hard way that old fuel is trouble.  I now would rather throw it
    away than take a chance that it might cause my engine to run
    unreliably.
    
    Charlie
    

    RE:.8
      When you talk about oiling after use are you saying put some
    oil down through the cab and crank the prop a few times? The
    reason I ask this is that is what I do with the 2 stroke engines.
    I use a light oil to keep it from rusting when the airplane sits
    for a little while(I don't get out as much as I'd like to).

                                           KEEP'EM FLYING
                                           JERRY

		G'day

	4 strokes have a vent in the crankase to prevent pressure
	build up from gasses coming past the piston. Squirt lots
	of after-run oil in here.....
                     
	cheers

	bob

    With a 2-stroke, you get good oiling by dumping it into the carb
    and turning the enging over.  That's because the fuel/ air mixture
    goes down the crank and into the lower end before going up the intake
    ports and into the combustion chamber.  In a 4-stroke, the fuel/
    air mix goes right from the carb to the intake valve (just like
    in your car).  Only the oil that gets forced by the piston ring
    will get down to the bottom end and the crank bearings.  The crank
    bearings are the major rust problem.  Most of the oil if put in
    the carb will stay above the piston and go out the exhaust valve
    into the muffler.  This does protect the valves and the seats, but
    not the critical crank and camshaft bearings.  On a 4-stroke, you
    must oil it through the crankcase vent.  Don't skimp on oil, and
    turn the motor over to distribute the oil around.
    
    CHARLIE
     

    
    
           THANK'S FOR THE INFO GUY'S.I'VE BEEN ON VACATION 
           FOR A WEEK AND STARTED ON MY ETRICH TAUBE AND I'LL
           HAVE IT READY FOR THE SPRING.I THINK I'M GOING
           TO PUT THE O.S. 48FS IN IT AND HOLD MY BREATH.
    
    
                                       KEEP'EM FLYING
                                       JERRY

    
    	Just to re-kindle an old flame....
    
    
    	I'm getting ready to burn in my OS90FS.  From what I here, I
    can go ahead and use my two stroke fuel for now (at least while
    it is mounted outside the plane).
    
    	My question is, How is a four stroke oiled?  Is there an oil
    reservoir in the engine, or is it oiled basically like a two stroke?
    
    	Just alittle background on the operation of a four stroke.
    
    
    Thanks...
    
    Ken

    Ken,
    
    I've had great luck with both my four cycle engines an O.S. .40
    and a .48 Surpass, what pulling power that .48 has!  Anyway, back
    to your question, four cycles are lubricated like the two cycles
    but in the two cycle the fuel is drawn into the crankcase then forced
    into the cylinder during the intake cycle.  Lubrication in a four
    cycle comes from the top down - primarily from blow-by past the
    piston on the power stroke.
    
    You're right on using two stroke fuel, both of my fours like the
    stuff and the extra oil doesn't hurt!  A note of caution ALWAYS
    use and after run oil, since the crank bearings are not as accessable
    to lubrication as a two cycle they can rust in some circumstances
    if unburnt fuel (nitro in particular) is allowed to collect down
    there.  Try this - use WD-40, LPS-3 or Marvel Mystery Oil (my choice),
    squirt some in the carb, unscrew the plug and pour some onto the
    top of the piston, and hand crank that sucker a few times to make
    sure all the oil is evenly distributed.
    
    My FS 40 is three years old and runs like a champ.
    
       --|--             Happy (con)Trails!
        (O)             
________/ \_______       Scott Cox
    

    	Thanks for the info Scott.  By the way, it will be mounted inverted
    and I haven't even burned it in yet.  But if two stroke fuel doesn't
    hurt it, I'll bench test it hopefully this weekend.
    
    Ken

    
    Does anybody out there have any experience with or observations
    concerning the Webra 4 Strokes, particularly the Webra 80?  Seems
    a bit unconventional compared to most other 4 Stroke engines, due
    to it's belt driven valves and single induction/exhaust system.
    
    Also, seems on the inexpensive side, compared to other similar engines.
    With Webra 4 Strokes, do you get what you pay for?
    
    Thanks,
    
    Chris
    
    (The other Cavanaugh in this notefile!)
    

    Dan,
    
    I wish you the sincerest best 'o luck.  I know many modelers who
    have great luck with 4-cycles but, to a higher percentage than with
    2-strokes, I see many who fritter away their flying day "fiddling"
    with their ornery 4-strokes too.  Hope you join the ranks of the
    former.  The studied, judicious approach you plan should go a long
    way toward assuring this...it could easily be that those I observe
    having problems have not taken such an approach and might have problems
    with a 2-cycle as well.
    
    My greatest objection to 4-strokes remains the lack of [comparable
    to similar sized 2-stroke] power, increased weight and complexity.
    Today's 4-strokes cannot even claim the less-noise feature as they've
    become much louder as demand for power was responded to.  Therefore,
    I'm at a loss to figger' just _what_ the advantage is supposed to
    be.    

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

    
    There is only one advantage (if you want to call it that) with running
    a 4 stroker. That being "scale sound". Not noise. granted on a DB
    meter the 4 stroker is as loud or louder and the 2 stroke but the
    percieved noise level is less. Like Dan said it's the frequency
    that's different. Not the noise. When I way scale sound I mean
    something other than the whine of a 2 stroker. 4 strokes sound little
    like a scale power plant but on a scale on one to ten the rate a
    3 in scale sound with the 2 stroker rating a 1. 
    I to have seen those that seem to only fiddle with their 4 stroke
    engines. My experience has found that these are the same types of
    guys who open up the transmitters and receivers just to see what
    the look like. They are the tinkerers. I have owned four 4 stroke
    power plants. A 40 os,60 enya,90 os and a 120 os. I haven't run
    the 90 os but all of the others ran well. I didn't fiddle wit them.
    All I did was check the valve clearance when new, ran it on a stand
    for a couple of tanks and then ran them in a plane. I never had
    any problems.
    
    
    Tom

        Re:< Note 411.18 by PNO::CASEYA "THE DESERT RAT (I-RC-AV8)" >

        Rat!
        
                It must  be the sun shining on your bald foreheads or the
        dry desert air  that  causes  your four strokes to be ornery.  Op
        here they run like champs, don't kick back and are just wonderful
        to work with.
        
                An advantage to four strokes  is  the  greater torque and
        accelleration  that you get with the  steeper  props  running  at
        lower RPMs.
        
                Don't talk ill about four strokes.
        
                      _ 
                     / |
        |  _====____/==|
        |-/____________|
        |    |        o \
             O           \ 
                          O
         Hang in there! o_|_
                          |
             Anker      \_|_/

    Re: .21, Anker,
    
    For those of y'all who love them thar' 4-cycle critters, I'm gonna
    do ya's a service; to enhance availability of the overweight,
    underpowered, fiddly (to borrow a term from our UK buddies) beasties,
    I promise never _ever_ to buy one!  :B^)    

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

RE: .22  -< 4-bangers Suck. >-

    Here we go again!  I have to agree with Eric on all counts, and
    admit that I enjoy my Enya .46 4-stroker but it can't come close
    to the 2-stroke reliability, ease of adjustment, etc.  I don't
    mind replacing bearings and grinding valves - a necessary part of
    living with 4-strokers, and I'm surprised when I hear people say
    they are just as realiable and easy to use as 2-strokes.
    
    I'll continue to use 2- and 4- stroke engines because I love the realistic
    sound, lack of messy oil, and reduced fuel consumption of the 4-strokes
    but when I get tired of pampering the 4-stroker it's nice to crank
    up the old reliable OS .45FSR!

    I love these arguments!
    
    Bill

    Dan,
    
    Don't you know better than to put a naked finger in front of a four
    stroke?  Just when I thought you were salvagable. :-)
    
    Really, there is nothin shameful about using a chicken stick!
    
    Glad you survived (and earned some respect),
    
    Chris

    Dan,
    
    A short piece of old stiff garden hose makes an excellent 'chicken-
    stick.'  Just find an old junk hose and yer' set fer' life.  Newer,
    more flexible hose will require a dowell be inserted inside but
    this isn't necessary with the old stuff and less prop damage results
    as well.   

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

    Al,
    
    I doubt that Dan can find his old hose, let alone dig it out.
    
    Isn't medical science wonderful, who would think that it could be
    fixed with a dowel?
    
    Chris

    Geeze !

    You guys should spend less time "Hose"-ing each other !

    I don't know where you ol'boys are com'n from but what I did seen
    is that the outside of a chik'n stix get rathered cut up. I'd
    tink's tat you'al would be better careful what tat ther stik you'd
    use in them there engines. Do no but thinks a doct'r be'd less painful.
    :-)
    
    
    I have seen the plastic and a dowl supported chicken stick chopped
    off by a running engine with those black props. The best chicken
    stick I ever saw was one made up of two air lines one inside the
    other. Can be had at most DEC plant maintanance offices.
    
    
    
    
    Tom 

    I have heard of using tooth paste as the lapping compound.
    
    
    
    Tom

Re: < Note 411.36 by SA1794::TENEROWICZT >

>    I have heard of using tooth paste as the lapping compound.
    
I use it all the time for other lapping jobs on model engines. It has the
advantage that it is clean and you don't get yourself or the workshop covered in
rouge.

There are diamond pastes that are better but you talk real money and for the
amount of lapping most modellers do it is not worth the expense.

John.

Try this - it is cheaper and fun.

Buy a can of Restone (not sure of the spelling).
It is an engine additive available in almost every
automotive section of department stores.

Put it in an oil can and put a piece of old fuel line
on the nipple of the oil can.

Start up that .61 and when it is running squirt some
of this stuff in the carb.  This will be tricky cause
the wind from the fan will fight your floppy fuel line.

It will smoke like crazy and loose a few RPM for a few seconds.

Repeat this 4 or five time.

Shut the engine down and feel the compression - you will
be amazed!

A guy named Jim of the Wachusettes Barnstormers did this to
my Saito 45 one day at the field and I have had a can of
Restone (sp) on my work bench ever since.

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

    
    Kay -
    Did the guy tell you what the stuff does?  Sounds like it must
    put some kind of coating on everything.  I've heard of such things
    (I think they mention the coating is teflon) but wondered if they
    really worked very long, and what the side-effects are.  How long
    did the good compression last after treatment?  Any idea if it
    hurts the bearings?
    
    Bill

    Yipes !

    What your describing is *NO* substitute for lapping valves.  Restone is
    simply gumming up the works.  The fact that the compression goes up is
    no bargain, so does internal friction.  Also, all that smoke you see is
    coating your valve, seats and stems with lots and lots of carbon (lets not
    forget the entire inside of the combustion chamber, either).  This
    sounds like a real bad shortcut to me.  In general, I think its safe to
    say that whats good/bad for an automobile engine is good/bad for a model
    engine.  I don't know a lot about model engines, but I do know that
    there is no "liquid" diet you can feed an auto engine that will improve
    compression (there are chemicals that will clean carbonized deposits
    from the combustion chamber and valve seats, and these could yield an
    improvment in compression in a really dirty, gummy motor, but they
    aren't substitutes for proper dissasembly and cleaning.  typically, they
    get used in junkers that run REAL bad, and aren't worth the time and
    expense of fixing right).

    Don't fool yourself into thinking this is a fix.  Lapping valves
    involves grinding the valve against the valve seat, the idea is to have
    a "perfect match" by "customizing" each seat for it's particular valve.
     You can't do that without disassembling the motor.  If this Restone
    stuff  is doing anything, its making it MORE likely that you're gonna
    need to grind valve seats, not making it so that you DON'T !

    Dan,
    	My OS91 Surpass turns about 8500 to 9000 on the ground with
    a 14/8 prop.  It probably gets closer to 10k in the air unloaded.
    I'd see how it runs and if it makes good power, don't take it apart
    yet.  Wait til you really don't have compression cold and you are
    sure that the valves are leaking.  Check the valve lash though.
    The published rpm's are the recommended useful range.  You don't
    have to be at the top of this for the engine to be good.  You will
    only turn max rpm's with the minimum recommended load in the air.
    The valve train and breathing limit the useful rpm's on these engines.
    Torque falls off before the maximum RPM.
    
    Charlie
    

>    Yipes !
>
>    What your describing is *NO* substitute for lapping valves.  Restone is
>    simply gumming up the works.  The fact that the compression goes up is

I believe that it is not gumming up the works - in fact it is cleaning up
the works.  The four strokes don't have much compression because the valves
aren't seating properly cause the valves are gummed up and dirt is present.

This stuff is the moral equivalent of after run oil.

>    no bargain, so does internal friction.  Also, all that smoke you see is
>    coating your valve, seats and stems with lots and lots of carbon (lets not
>    forget the entire inside of the combustion chamber, either).  This

all two cycle engines smoke because of the oil in the fuel - is that carbon?

>    sounds like a real bad shortcut to me.  In general, I think its safe to
>    say that whats good/bad for an automobile engine is good/bad for a model

and this stuff is made for auto engines.

>    engine.  I don't know a lot about model engines, but I do know that
>    there is no "liquid" diet you can feed an auto engine that will improve
>    compression (there are chemicals that will clean carbonized deposits

I bet this stuff will - although perhaps only for a short time.

>    from the combustion chamber and valve seats, and these could yield an
>    improvement in compression in a really dirty, gummy motor, but they
>    aren't substitutes for proper disassembly and cleaning.  typically, they
>    get used in junkers that run REAL bad, and aren't worth the time and
>    expense of fixing right).
>
>    Don't fool yourself into thinking this is a fix.  Lapping valves
>    involves grinding the valve against the valve seat, the idea is to have
>    a "perfect match" by "customizing" each seat for it's particular valve.
>     You can't do that without disassembling the motor.  If this Restone
>    stuff  is doing anything, its making it MORE likely that you're gonna
>    need to grind valve seats, not making it so that you DON'T !

Seems like all these little four strokes loose their compression after a flight
or two - it really doesn't seem to hurt anything - I'll bet they actually have
plenty of compression when their running but when you spin them by hand the
just seem to have lost it - and and valves are adjusted within spec.

If the apparent lack of compression bothers you pour oil down the glow
plug - or squirt Restone in the carb when it's running.

This stuff is good - try it.

If you think it actually causes harm - sue the company (and STP while your
at it) but I will volunteer to testify on their behalf.

Gosh I love controversy.

This isn't the correct note but - remember there is an auction tonight
in Chelmsford - see Dan Snow for details.  I'll be there selling my
EZ-1 that Dan Snow built and the RAM simple cycler.  Kevin is taking a
slightly damaged but beautiful Newport.

Now how do I convince my wife to let me work longer on the Berliner-Joyce
tomorrow evening because I was cheated out of my RC time by attending
the Auction tonight?

Gotta go - I have to sneak around the parking lot squirting Restone
in every gas tank that isn't locked - a person can never have too much
compression you know :-)

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

    Sheesh ! Kay !

    I didn't say it wouldn't work.  All I was trying to get across was that
    there are no short cuts.  It's a Pay Me Now Or Pay Me Later kind of
    proposition.  I believe that there is always time to do it right.  Many
    people (including you, apparently 8^) ) believe that there is always
    time to do it over.  Difference in philosophy.  Oh well. 

    Engines lose compression as a result of, in general, three causes.  One
    is damage to the engine, in the form of burnt valves, cracked
    heads/cylinders, blown gaskets, burnt rings.  Two is wear, in the form
    of loosened tolerances between piston/rings/cylinder and valve/valve
    seats.  Three is combustion byproducts that tend to build up on both the
    intake and exhaust valves, affecting their ability to form a good seal. 

    The only thing that can be remedied through the introduction of foriegn
    substances to the intake system is combustion byproduct buildup.  I
    don't believe, nor can you ever convince me, that worn/pitted valves and
    seats can be improved by the addition of a liquid that "fills the
    holes".  PAH! I own this bridge in Brooklyn, wanna buy it ?  Metallurgy
    just doesn't work that way.

    The problem with just adding gunk to clean off the valves and seats is
    that, because there has been a significant buildup of deposits, there is
    also a significant amount of wear.  You don't remedy the wear with an
    additive, you remedy it with a substance, applied once the motor has
    been removed from the plane, called "Elbow Grease".  You might see an
    improvment in compression by adding this goo, you might see a decrease
    (sometimes the carbonized buildup actually helps fill nicks in the
    seats, and removing it leaves an opening when the valve is seated), but
    you won't get anything like the results you'de get if you did the job
    properly. 

    If, on the otherhand, this stuff is actually supposed to work by
    "filling the holes" of pitted metal valves, I ask you to consider what
    it is doing to the rest of the motor ?  How about the honing at the
    interface between the piston and cylider wall ?  What is is leaving on
    your carberator venturi ?  What is it doing to the glow plug, intake
    port, etc ? Surely, if it can fill in tiny pits in a valve seat, it can
    build up on just about any other surface it contacts. 

    Since I don't fly gas, I can't speak for gas plane owners, but I do
    drive a car, and I would never consider this sort of thing as a remedy.
    Its kind of like oatmeal in the radiator to plug a leak, or sawdust in
    the transmission to quiet it down.  All you are doing, in the long
    range, is shortchanging yourself, or cheating the person to whom you
    sell your "legacy".

    As for the question of smoke from 2 cycle engines, yes it is mostly
    carbon, though there is a goodly amount of unburned oil as well.

    












                                Your turn

                               Randy (8^D)

    The main problem with the little 4-strokes we have is the scale
    of things.  It's hard to get those tiny valves to seal well and
    it only takes a little piece of carbon to hang the valve open and
    no compression.  I agree with Kay that most of the time, you get
    the compression when it's running.  I've seen guys run 4-strokes
    that appeared to have zero compression and they seem to be fine
    once they're started.  I've seen compression come and go very quickly.
    The main problem is that if the compression is low, starting will
    be difficult if not impossible without a starter.  Since most people
    use a starter with 4-strokes they usually get them running.  The
    thing that hangs the valves is carbon from burning oil.  THis is
    aggrivated by running too rich with two stroke fuel which has 20%
    oil in it.  The valve seats are brass which is very soft so the
    valve closing on a piece of carbon can damage the seat.  
    	If Kay's wondor stuff removes carbon, then it may be fine to
    use it once in awhile.  If the seats get damaged, grinding will
    be required.
    
    Charlie
    

>< Note 411.46 by LEDS::WATT >
>                         -< Kay's Method Might be OK >-

I'm kind of hoping John Chadd will chime in on this one as I assume everyone
here will honor and respect his opinion.

Speaking of experts - as most of you know I sent my brand new old OS.61
black head to California to be checked out by Dave Shadel of Performance 
Specialties in Carlsbad because I thought I had a bent crank.

He wrote back

============================================================================
	Your engine has been completely disassembled, cleaned, inspected,
and test run.  It looks good.  No problems other than being filthy.
There is some raw fuel damage to some of the parts (dark discoloration) but
this won't affect operation.  

	Hope we can help you again in the future.

=========================================================================
I called and asked about the bent crank and if a dirty engine could cause 
vibration.  He said no but he checked the crank on some device (I forget what)
and it is OK.  He asked what kind of motor mount I had and I said a nylon one.
He said never mount anything bigger than a .40 on a nylon mount - use aluminum.
I asked what about the new noise saving rubber mounts - he said he didn't
believe in them.  He also said some engines can't be balanced so what you
can do is if it vibrates with a good prop - get one that is out of balance
and take out the glow plug and stop the piston at TDC and hang the prop
on with the heavy end down (opposite the piston).  If it gets worse reverse
the prop.

I asked what I should be doing different in the area of cleaning and he
was a little vague but said for an engine to be as dirty as mine it had
to be neglected pretty bad.

So that proves to me beyond reasonable doubt - I'm far form an engine expert.

I wonder if STP makes something I can spray down the carb that will clean
the outside and inside of the engine at the same time :-)

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

    
    
    What if anything does anyboy know about the Enya 80 4 stroke? I
    understand that it's in the Enya 60 4/stroke case. How does it
    run? Power? Comparitive size to the OS/Enya 60 4 strokers?
    
    
    Tom

    Dan,
    	We had several guys have the same problem with Power Blast fuel
    and 4-strokes.  Fred Zayas went through a couple of FS40 heads
    probably due to the extra rust inhibiter that Tom was putting into
    his fuel.  It caused severe detonation and carbon deposits.  Eventually
    the valves stick and the seats get damaged.  No more Blast for me.
    I used to use it in my 2-strokes exclusively but I don't trust it
    anymore.  I can get Red Max mail order for the same or less anyway.
    Hope you have good luck with the OS 61.
    
    Charlie
    

    Dan, I've been tell'in you about that old adage fer a while now.
    But ya got to experiance it to believe in it.. Welcome aboard to
    the "Ya pay the bucks, ya get's the quality club". (Well almost,
    theirs still lemons out there for big bucks.)
                                                
    
    
    						Dave
    

    Sounds like a straight 80% alcohol, 20% oil fuel mix.
    
    Tom

Don't like that idea much Dan. The problem is are you sure all the methanol is 
out of the engine when it Quits. Another point is the castor gums up the 
engine if it not used regularly and you can end up with other problems. 

I know of people who put 2-5% of castor in the fuel in addition to the normal 
synthetic to MINIMISE the corrosion. It work's but it does only MINIMISE the 
corrosion not eliminate it.

The best option is to  use a good after run oil after each days flying turning 
the engine over with the starter for about 15sec to ensure it is completely 
through the engine.

John.

    Way to go John!  Congratulations!
    
    I'm real glad to hear it flew nice.  I'm almost that positive mine
    will perform that nicely.  The only problem is I can't get that
    !*&!!*! OS.90 to run!
    
    I had it running all last winter with no problems.  After I put
    it in the MONK I couldn't get it to run properly because;
    
    	1.  I had it inverted (not the real problem) and had the fuel
    	    fed through my Kwik Fueler Valve (which was also not the
    	    problem) and didn't have a muffler for backpressure hooked
    	    up so I plugged up the breather tube.  This caused the 
    	    choking of the engine.  I didn't realize it so I kept ad-
            justing the needle valve.  Finally gave up.
    
    	--In short, I apparently adjusted the needle valve way out of
    	  whack!
    
    	2.  After getting it home, I noticed my throttle arm on the
    	    carb was loose, so I tightened the little screw inside
    	    the barrell!  Come to find out, that is the mixture ad-
    	    justment, and I don't know where abouts it was factory
    	    set.
    
    	--In short, my mixture adjustment screw is not set to factory
    	  specs anymore.  Any ideas are welcome.
    
    
    I did have it running a week ago in my cellar, but the fumes were
    getting too much.  When on the next day I took it out for flight
    (not in the MONK) it woulnd't kick!  I've changed the plug, adjusted
    the valves and prayed over it, but no luck.
    
    One quick question to anyone holding the answer.....
    	When starting a 4-stroker, should the carb be partially opened
    as with the 2-strokes or fully open?
    
    
    Anyhow, I'm putting all the radio gear back into the MONK in hopes
    of flying this weekend!  Hope I'm as fortunate as you and Carl.
    
    Ken
    
    
    PS.  Carl, long time no hear!  Been MONKeying around lately?

        Re:                    <<< Note 508.114 by VTCOWS::SOUTIERE >>>

        Ken,
        
                If you  have any of the original documentation, it should
        tell you how to set the needle valves initially.
        
                Its essential that  you make the mixture VERY rich if you
        don't have the instructions.  Get the sucker running, even if you
        have to pour fuel into  the  cylinder.    Then if it starts, runs
        fater and faster and then dies  you  are  still  too lean.  If it
        coughs smokes and rattles, but still keeps running  you  have  it
        too rich.  My experience is that four strokers like being started
        at fairly low idle.  In winter you sim ply won't get them running
        at  all if the throttle is open.  Once they start  you  let  them
        warm up a little at low idle wioth the glow plug driver attached.
        When  it  runs without the glow driver let it run a little longer
        and then  you  can  start opening it up.  Your problem could have
        been that it was too wide open.
        
        Anker

    Ken,
    
       Got ya covered on the instructions for initial setup for the OS.
    I was surprised that the carbs are setup the same on both the OS .46
    and .61 sf two strokers as they are in the .90's.  Here's the quicky on
    the setup.  Open the throttle full.  With a light shining down the carb
    adjust the mixture screw until the second largest "ridge" (there is
    only two) is tangent to the side of the throttle wall.  You'll
    definitely need to make sure the valves are dead on.  If the timing
    hasn't been changed it will start.  Call me up if I didn't make sense.
    I work swings so call after 4:00 pm MST....dtn 592-5456.
    
    Hope this helps ya.
    
    BTW: hows the cuts healing?
    
    John C.     

    Thanks Anker and John for the info.  
    
    Last night with the assistance of my brother I managed to get the
    .90 running!  
    
    Started out with the needle valve 1.5 turns out and worked it out
    from there.  Using a chicken stick I did notice HIGH compression.
    That prop kicked the stick so hard it hurt my hand.  Anyways, after
    a few coughs I used an electric starter and low an behold it started!
    I adjusted the needle to the best spot and then went and adjusted
    the mixture valve.  I think I cranked it in 2-3 full turns as the
    engine kept rev'ing up which each twist of the screwdriver.  So
    I basically have it set within limits.  So now I am transfering
    all the gear back into the MUNK in hopes of getting her maiden voyage
    this weekend.
    
    John, the finger is a bit sore, but healing fine.  Good cut though!
    
    Ken

    Ken,
    
        Forgot to tell ya how to fine tune the mixture setting.  After you
    get it close to idle, slowly pinch the fuel line, one of two things
    will happen.  1) the engine will increase rpms, 2) engine will die
    abruptly.  If #1 happens turn the mixture screw clockwise 45 degrees,
    then try again.  Ideally you want it to increase slightly indicating	
    just a tad rich...  If #2 happens your too lean..open (counter
    clockwise) 90 degrees and repeat process.  Just remember rich=clockwise
    lean=counter clockwise.  OS recommends not turning more than 90 degrees
    at a time...use your own judgement.
    
        Looks like I won't be flying for a couple of weeks.  We're supposed
    to be getting some snow (finally) tonight.
    
        Let ya know when I get to go up next.
    
    John C.
    

    Could someone do a quick measurement on an OS91 Surpass for me. Could you
    tell me the minimum clearance distance from the back of the spinner to  the
    firewall. 
    
    I know the OS engine sheet gives dimensions but not to the back of the carb.
    
    I was hoping to put a OS91 on my Acro Wot but I suspect that I should have
    shortened the nose for the extra engine length. Then the 91 was sort of an
    after thought but if I could get it in it would be super. 
    
    Eric();
    

    
    
        Eric Henderson may be able to help you. He has a 91 Surpass in his
    Acro-Wot, but I don't know what modifications were needed. I will 
    measure the distance for you tonight on my 91. It is bolted in a motor
    mount awaiting a plane, so it should only take a second.
    
                                               Dan W.
    

    
    
       I took the measurement today. It is 4 5/8" from the back of the carb
    to the front of the spinner plate. This is without the choke installed.
    Add another 1/4 to 3/8" if you will be using the choke. The 4 5/8"
    measurement allows about 1/16 " clearance from the mount to back of the
    carb.
       Another consideration is weight. In case you are not aware of the
    weight if the 91, is weighs about 22.5 oz.
       As I mentioned before, Eric H. is a better source of info, but I 
    understand he is on vacation.
    
                                   Hope this helped,
    
                                           Dan W.

    I was told by a fellow flyer that runnnig 2-stroke fuel in a 4-stroke
    engine causes the engine to run hotter, thery-by hurting the engine in 
    the long run.
    
    Is this true?  Should I be running only 4-stroke fuel?
    
    
    Ken

    Re: .-1, Ken,
    
    I'll leave the final word to the 4-stroke experts but my understanding
    is that 2-stroke fuel contains _MORE_ lubricant that 4-stroke so, if
    anything, the 4-stroke engine should actually run cooler on 2-stroke
    fuel.  I'd speculate a slight drop in top-end performance owing to the
    higher percentage of oil in the fuel but wouldn't expect any damage. 
    
    Now, the converse of this should be that 4-stroke fuel may well damage
    a 2-stroke engine due to inadequate lubricant content.  How 'bout it,
    4-strokers, am I anywhere near the mark here....??
						 __
				|      |        / |\	   	       
      	         \|/		|______|__(o/--/  | \	   	       
      | |        00	       <|  ~~~  ____ 04 ---- | --------------------
    |_|_|        (O>o		|\)____/___|\_____|_/	   Adios amigos, Al
      |     \__(O_\_	        |	  |___/	 o	   (The Desert Rat)

    All I can say for sure is that OS recommends 2-stroke fuel in all of
    their new 4-stroke engines.  The only disadvantage I know of is quicker
    carbon buildup on the valves and valve stems due to burning of more
    lubricant.  Bearing life and ring life should be improved, and power
    might be down a tad.  I've used both in my OS 4-strokes with no
    noticable difference in performance.  Methanol does provide much of the
    cooling of our engines due to it's high latent heat of vaporization. 
    That's why a lean run makes the engine so much hotter.  All alcohol
    racing engines suffer from heat problems if they get run lean, but run
    great rich. 
    
    Charlie
    

Re: Note 411.65

Like Al, I see no reason why a 4st should run hotter with 2st fuel with extra
lubricant. The only factors I see effecting the temperature could be if the
nitro content is down in the 2st fuel it may decrease the needle margin and
give a hotter run from in-flight mixture variation. You may also need to adjust
the compression for the extra lubricant by adding or removing shims. 

While I prefer and recommend 100% synthetic oil in 2st fuel I recommend some of
the lubricant should be castor (about 5%) for use in 4st engines. 4st's run
hotter than 2st, if you use 100% synthetic you can on a lean run vaporise all 
the oil at loose lubrication. The 5% castor gives you some safety margin. 

If you wish to use the same fuel in 2st and 4st I suggest a mixture of 

	5-10% Nitro,  10% Synthetic oil, 5% Castor oil, + methanol.

The proviso is you must use a good synthetic designed for high temperature 
applications and be careful not to have a lean run. (always be one click rich)

John

    What a wealth of information, thanks guys.
    
    I am using Tower Hobbies "Cool Power" 10% Sport fuel.  I haven't seen
    any problems using it either.  But when I was told that 2-stroke fuel
    would ruin the engine, I got nervous.
    
    Again, thanks for the info, I feel much better now.
    
    Ken

At our club swap meeting last Tuesday, I picked up an OS .40 four
cycle -- not the Surpass.  Got it for a song, and besides its so
darn cute!

Tried running it last nite and came up with some questions.  I
had trouble starting it, and when I pulled the plug, I found that
it wasn't lit even with the driver sitting in the middle of the
RC range.  So I cranked it up full and the plug glowed ok and I
started the engine fine.  First question: it looked like a Fox
Miracle plug, but did't act like one, since the Miracle drives
fine with the needle in the RC range.  Is this a four stroke
plug, do they need more drive?

After I got it running I noticed that there was a lot more
vibration than I got with my 2-cyc.  In fact, the first time I
got it running I shook the mounting screws on my test bed loose
almost immediately.  After cranking them down hard it was OK, but
it still was lifting the saw-horse I had it mounted on more than
the 2-cyc.  Is this normal?

Thirdly, my OS .40 FP barely pulls the PT; since the 4-cyc is
supposedly weaker, can I assume that its too small for the PT?
If you look closely at the PT, they do recommend the OS .40 4-cyc
for it,  but my experience with the FP says otherwise.  I do
suspect that my FP is a dog, since the Fox .36 pulls it just
fine.

I sure like the sound of the 4-cyc putting!

    
    
        I also picked up an FS-40 at an auction last year. I ran miracle
    plugs in mine without any problem. As far as the vibration goes, it was
    a very smooth running engine with a nice put-put sound.
        It is probably too small for the PT-40. It is only rated at .5 hp,
    which is only 1/2 of the 40-FP. I had it installed in an Ace 4-40 which
    was designed around this exact engine. It was a nice put-put plane,
    but the takeoff and climb performance was marginal. I think the next
    plane I try it in will be more of a .25 size aircraft.
         I was using an 11/6 and an 11/7.5 prop with ggod results.
    
         Nice engine, but weak.
                                                                  

    The original FS-40 was much less powerful than the new Surpass
    versions.  It would not fly a PT-40.  You might have a higher voltage
    glow plug.  They used to make 2 volt ones for use with wet cells.  A
    regular miracle plug should glow just fine with 1.2 volts.  This engine
    will fly a 25 size plane ok but it really is pretty weak in the power
    department.  They run great though.
    
    
    Charlie
    

OK.  This last weekend I checked things over and found that my
field box battery is not putting out enough poop, so I recharged
it and it looked better.  Didn't try the 4c plug on it yet
though, I'll give it a look tonite.

Thanks for the advice on the PT40.  I have been very pleased with
this plane, enthusastic to say the least; its a wonderful ship.
But it does have two faults: it can be slowed easily into the
region where the ailerons have no effect, both on takeoff and
landing, and it does soak up power on takeoff.  Once its in the
air I can pull power back to less than half throttle and it'll
fly comfortably.

Last week I counted up my flights for the year; a little over 40
TOTAL so far, and about 30 on the PT.  Pretty dismal, but it does
make me feel better for the lack of progress I've made.
Unfortunately, the chances for changing this situation are near
zero.

Anyway, I'd like to put the 4c on the PT just for kicks, but I
decided to wait until I'm a little more bored with the PT -- or
to put it more accurately, until I feel more comfortable flying
it.  Right now, the 4c is sitting in its box, but I'll probably
put it into the Tutor soon, where it should be near ideal.

From what I've heard about the APC props, it just might make the
difference between lugging into the air and taking off safely if
I put one on the 4c if and when it gets into the PT. 

    I have an opportunity to pick up a 9' 1/4 scale cub with a Saito 1.20
    4c in it. I was wondering if there was anything I needed to worry about
    with the Saito (parts availability, design weaknesses) and what a
    reasonable price would be for this engine/plane (built and flown but
    not crashed). This was one of our club instructor's planes and he wants
    to move up to the Balsa USA 1/3 scale kit.

   Has anyone out there had to re-adjust the gaps between the rocker arms and
   the valves on an OS91 Surpass ? I had a look at mine recently and found them
   to in the 9 thou range. The recommended range is between 1.5 and 4 thou. I
   adjusted them to approx 2 thou. The reason being that I noticed a rattle
   lately (not that it suddenly appeared) that was out of the ordinary. Yet to
   start it up though to see if that was my problem - but I suspect that it was.
   I would expect that I would have seen a drop off in power by can't really
   notice anything maybe a drop of 400 rpm max.
   
   Anyone else have any comments ? 
   
   Eric();
   

    
          I can't say I have honestly adjusted the valves on a 91 Surpass,
       but I just checked mine on Saturday. The spec was between 4 and 10
       thousands/inch. The instructions with the engine
       say that the 4 thousands should pass through the gap, but the
       10 should not. That is exactly where mine were, so I left them
       alone. I put in six flights on the engine yesterday, and it ran
       flawlessly.
          Are you sure the valves were in the proper position, and cold
       before checking your setting? I t may be something other than
       valve clearance.
    
                                                                  Dan
    

    I have a 91 surpass too (in a Big Lift from Multiplex) an I'm
    adjusting the valve clearance ecactly like you stated - works wery well 
    and very much
    
    harrY

    Just out of interest. What are the minimum idle revs that you guys with OS91
    Surpass 4 strokes are getting ? I thought I heard somewhere, maybe in the
    DECRCM videos, that someone was getting as low as 1500 rpm - I am typically
    getting down to about 3000 rpm. Then again the low rpm is to some extent 
    fuel dependant - nitro content. I generally use the pink gin stuff with 15%
    nitro content. I would really like to drop it down a another 100-1500 revs.
    Any comments ?
    Regards,
    
    Eric from the Green Isle.

    Eric,
    
    My .91 running a 13-10 prop idle smoothly at 1800-1900.  I too am
    running 15% nitro.  You maybe loading up when idling.  Just adjust your
    idle mixture and you should be able to get it down further.
    
    John

    Eric,
    	What glow plug are you using?  I've found a big difference in the
    idle reliability with different plugs.  I have found none that work as
    well as the OS type F plugs that come with the engines.  The FOX
    Miracle plug gives a great idle but seems to be too hot - does not run
    well at top end.  The K&B plug seems to be too cool and the idle is
    terrible.  With the OS plug, you should get only a slight drop in idle
    RPM when you remove the starting battery.  I have not measured the idle
    RPM of my 91 Surpass, but I'd suspect it's slightly under 2000 rpm.
    	The type and diameter of the prop also makes a difference.  I get a
    better idle with a larger diameter, heavy prop like the Graupner.  I am
    also running 15% nitro in mine.
    	John's suggestion to check the idle mixture is right on.  It has to
    be right or you will not get a reliable idle.  Too lean and it will die
    when you advance the throttle, and too rich will cool the plug and it
    will stall.  Make sure your top end mixture is right before setting the
    idle mixture.  If you change the idle mixture much, go back and
    readjust the top end again.
    
    Charlie
    

    Charlie,
    
    I am using the OS type F. In the past I experimented with different
    plugs on my other engines until I got the right one but as regards
    the OS 91 I have always used the OS type. 
    
    As for propellors - I have used 11 x 7 and then progressed to 12 x 11
    which I use all the time - as you say the large the diameter (& the
    pitch) - one should get a lower and possibly better idle. I generally
    use the Graupner but do like the APC 12 x 11. The Graupner is, as you
    say, a fairly heavy prop and not as streamlined and quiet as the APC.
    Hence the APC does have a higher idle.
    
    I suspect (or know) that the idle mixture is too rich. I tend to avoid
    adjusting OS idle mixture settings cause in the past have found them
    fine. Pick up on advancing the throlle has never been a problem - it
    _never_ hesitates. I think the time has come to adjust the idle
    mixture. The engine does produce more blue smoke (more than I like and
    think acceptable) after starting and at idle - a sign that it is too
    rich. I have accepted this till now but now that I am looking for a
    lower idle its not acceptable. So this weekend I am going to adjust the
    idle screw to try and eliminate the smoke while maintaining the smooth
    consistant transition  to and from idle. This should get the idle rpm
    down. 
    
    Onother problem that I don't have, as can be seen on cheaper or bad
    carb designs is the lateral or sideways barrel movement - the OS91 carb
    is free of this. This would, if present, make consistant low throttle
    settings difficult - with the baerrel jumping around.
    
    I was out flying on Monday evening in 20-25 mph winds and found that I
    could walk the Acro-Wot in really slow. Thats fine but I would
    generally fly in 0-15 mph winds where there is little to help slowing
    the plane down. I find here that the plane would typically need 2 or 3
    times the length to land at a reasonable speed.
    
    I post my result and findings here !
    
    Thanks and Regards,
    
    Eric
    
    
    

    ERic,
    	I also use a 12 x 11 Graupner on my Panic.  You want to turn the
    mixture screw in (clockwise) to make the idle leaner.  Take it a little
    at a time and keep checking the top end mixture and the throttle
    response.  It should not smoke much at idle and it should not slow down
    and quit.  Throttle response should be smooth and quick.  If it
    hesitates when you advance the throttle, it's probably getting too lean
    at idle.  Make sure it's nice and warmed up before making adjustments
    especially if it's cold outside. (It was 34 at my house this morning.)
    
    Good Luck,
    	      Charlie
    

    Eric,
    
    You also might check the throttle stop screw.  It maybe stopping to
    soon.
    
    John

   Well, over the weekend I did some experimenting. I adjusted the rich screw
   setting such that I got the idle down to approx 2800-2900 rpm. I had a number
   of flights to see if it did not die when transitioning from a lengthy low
   idle to full throttle under load - no problems. The wind was 15-20 mph but it
   did come in a lot slower - it still remains to see how it helps in zero wind
   conditions. That said I was satisfied with my tweeking. All these adjustments
   were sort of put on hold when an irate farmer complained about a horse that
   bolted into a barbed wire fence - but we couldn't find the horse ! What we
   suspect is that he saw my car reg (not being a local Galway one) and had a go
   at seeing what he could take me for - but that all remains to be seen. My
   insurance will or should cover it - should it develop. Back to the engine...

   I just had time to try the nistarter on the glow plug...before the horse
   problem...
   I tried the idle with a NiStarter connected - got the idle down to approx
   2000 rpm - with no problem with transitioning as above. So I may rig up an
   on-board battery pull switch to bring in the nicad at low idle but I would
   like to avoid that if at all possible. Time to look for info via the keywords
   on on-board glowplug warmers !

   Thanks for the replies.

   Regards

   Eric.
    

    Eric,
    	The trick with on board glow is to use heavy enough wire and keep
    it short enough.  I use the very fine stranded wire that is used for
    electric planes.  I think it's #14.  I got an on board glow kit from
    Great Planes and the wire was too thin.  The engine was hard to start
    because the glow plug was not getting hot enough.  I had to replace all
    of the wire.  A microswitch and a small bellcrank came with the kit to
    control the glow.  I set mine up to activate at about 1/3 throttle
    since I start my engine at about that setting.  A 1200 MAH nicad will
    only run about 30 minutes, so you have to be careful not to leave it on
    too much.  My OS91 runs fine without on board glow with 15% nitro and
    an OS type F plug in it.
    
    Charlie

    Another question on the OS91 4-s...
    
    
    I have just rebuilt the engine with the replacement parts that I got
    but I have one question regarding the cam shaft insertion. 
    
    Does one insert the cam such that it lines up verticaly, with the piston
    at TDC, or in the center of the small blocks (at the end of the rods
    that actually touch the cam or otherwise ?
    
    Regards,
    
    Eric.

    Ok, I just purchased my first 4-stroker, on OS 120 Surpass, which I
    plan to install in the Top Flite P-51D Mustang.  This is one of the
    recommended engines according to the plans.  The first thing I noticed
    is that the engine has to be mounted inverted.  According to other
    replies to this note, as well as comments I've heard from others, this
    is not a particularly good arrangement.  Some say that the YS120 works
    better inverted.
    
    I plan to use on-board glow to overcome as much of this problem as
    possible.  Has anyone else used this engine inverted, with or without
    on-board glow?  What has been the experience with engine performance,
    especially idle?  SOme comments would be helpful.
    
    Thanks,
    Joe

    Joe,
    	I currently am running an OS 61SF ABC two cycle inverted in my
    Goldberg Chipmunk and can tell you that, at least with this two stroke,
    the engine tends to run lean at idle.  I did this for the same reason
    you have, the want for scale appearance.  It took a while to adjust the
    needle valve to where I wanted it and I don't touch it for any reason,
    which has worked very well.  I believe it leans out because the
    compression isn't quite enough to pull fuel "up" into the crankcase at
    low throttle.  I'm not sure but this might be amplified for a four 
    stroke engine due to the fact that it's pulling fuel only every other 
    stroke.  I always start the engine right side up(plane inverted)
    and let it warm up for a while.  The plane flies great, with the
    exception of running a little fast at low throttle(due to leaning at 
    idle I guessed) which makes landing more exciting. 
    	A couple of tips that I can give you are : Always use a fuel filler
    such as a Dubro because an inverted engine usually has the carb below
    the centerline of the fuel tank and, as you fill the tank, the fuel
    tends to freeflow down the line and into the carb and out the carb
    opening on to the ground.  To prevent this, I have a spare filler 
    nozzle that has been plugged at the hose end that I leave plugged in 
    the planes filler valve after the tank is fueled.  This shuts off 
    the fuel flow in the valve to the carb so you don't have a "puddle" 
    of fuel at your feet.  Then I remove it when I'm ready to start the 
    engine.  
    	Also, as you noted, a onboard glow system is a must.  I do run one
    on the Chipmunk and it seems to help tremendously. The first
    place fuel is going to go in the chamber is right to the glowplug,
    which is like throwing water on a fire and, with a four stroke that has
    a plug glowing at half the rate of a two cycle engine, this can be bad
    news.  The third thing to do is make sure that absolutely ALL the fuel
    is removed form the engine before calling it a day and use lots of
    after run oil.  Also try to store the plane inverted to keep the oil on
    the bearings.
    	I am currently working on a Top Flite Corsair, but was fortunate
    enough to find a four stroke .91 that I could mount sideways in a round
    cowling.  Unfortunately you don't have that luxury with a narrow cowl,
    but then again you are building one of my favorite war birds
                                                       
    Good luck,
    
    Carl

   Joe,
       "You never the easy path Eh?"
    
   I have used the OS120 inverted. Mine was the one before the pump. 
   Which one do you have?
   
   My first statement is that the 4-c will run just great inverted. I am 
   assuming that you have the pump version so that the fuel tank position 
   will not be an issue. 
   
   The secret of running an engine inverted is to get it running the 
   right way up FIRST. Get that idle right. Get the transition to full 
   throttle right etc. Do not even try running inverted until this has 
   been done. You will have ruled out most of the variables that can 
   cause you trouble. Best run it on the bench for a full hour. Running 
   an inverted engine rich in the air to run-it-in is just asking for a 
   dead stick situation to occur.
   
   Once the engine is run-in and the mixture set (See addendum on OS120 
   carburation problems), You can install it inverted. All you should 
   then have to do is adjust for a little perceived "Richness". With an 
   on-board-glow-lighter you may not even notice it. (I have used an on 
   board glow lighter. They are hazardous BTW and only last 20 min. when 
   engaged. I NEVER use them these days). 
   
   I usually stop an inverted engine after pinching the fuel line for a 
   few seconds to let the engine run partially dry when inverted to keep 
   the plug from filling up with fuel. Remote or on-board glow systems 
   have a big problem clearing a plug full of fuel. I have watched a plug 
   take 10 minutes to clear when full of fuel. (I do odd experiments like 
   this for no apparent reason - worry about me!).
   
   Starting is easy inverted. I have had more trouble with 2-c's in this 
   category. The 4-c opens an exhaust valve that allows the excess fuel 
   to be purged from the cylinder. This helps prevent hydro-locks and 
   does allow easy correction of the situation. (2-c's tend to need to 
   have the plug removed).
   
   Regards,
   
   Eric.
   
   
   addendum.
   
   The OS120 has a known problem with the pump giving too much fuel. 
   There are several well documented fixes for this problem. Run your 
   engine first and if you cannot tune it to transition from idle to full 
   bore, smoothly let us know.
   

    I would have recommended the YS120 STRONGLY over the OS.  I have the
    OS120 Surpass and I am not very happy with it.  The carb/pump setup is
    not great and the mid range is too rich.  That can cause problems
    inverted.  I have mine running right side up and it blows a big smoke
    cloud when I throttle up.  If I lean out the idle, it won't!  It has
    too much fuel pressure and the OS instructions caution you not to touch
    the pump under pain of death.  The YS has a great reputation on the
    other hand and I've seen plenty of them (most in pattern) running
    inverted without onboard glow.
    
    Charlie
    

    Thanks for the responses.
    
    OK, as I see it, this is an achievable task, but there some very
    specific cautions and procedures that must be observed.  So far I think
    they are all approachable, but discipline is a must, and this
    engine/installation can't be treated like a standard setup.  Meaning I
    can't get sloppy without inviting trouble.
    
    The OS 120 I bought is the standard unit, without pump.  Not sure from
    what's been said if I need this or not.  If I do, it's going to cost
    another half a bundle to add it.  I'd rather not have to do this.  As
    far as trading the OS for a YS, I haven't approached this yet, but I'm
    wondering if I'll get resistance from RC Buyers to doing a swap. 
    Broeder thinks this is a good engine inverted based on experiance
    several of his friends have had.
    
    Thanks again for the good advice.
    
    Regards,
    Joe

    Joe,
    	If you have a chance of trading it in and going for the YS I'd
    recommend doing it.  The YS (non airchamber is just fine) has a
    pressure fuel system that works great and it runs great inverted.  It
    is a much more accepted engine than the OS.  Take the pattern circuit:
    I have not seen a standard OS120 at a contest yet.  Some of the top
    guys are flying the OS supercharged engine but I'd bet that most are
    sponsored by OS.  On the other hand, the YS is the Dominant engine
    period!  (I don't have one yet. :-(  )  The other advantage of the YS
    is that your fellow HTA's have extensive experience with it.  I do not
    know anyone who is unhappy with the YS and I know several including
    myself that feel "Stuck" with the OS.  I'm not saying that the OS is a
    bad engine but the YS120 is superior in almost every way possible.  I
    do suspect that the non-pump version you have might run better but you
    will have to make sure that you mount the tank close to the firewall
    and at the proper height.  The pumped engines eliminate this
    requirement.  The tanks in my pattern ships are over the CG in the
    center of the wing.  This eliminates trim changes as the fuel burns
    off.  Remember that you carry a Pound of fuel in a 120 powered ship for
    a 10 minute flight.
    
    CHarlie
    

    If I build a scale model with an inverted engine I will use a YS120.
    With 15% nitro 2-c fuel it runs very well indeed. The non air chamber 
    engine goes for about $330 and will pull a 14 x 8 or a 13 x 10 with ease.
    
    The YS method of bringing fuel to the carb is not really a pumped system 
    it is a pressurized tank with a fuel metering device. The regulator lets 
    a little "Bump" of fuel through to teh carb everytime the crankshaft 
    completes one revolution. The more revs the more fuel. The instant the 
    revs decrease the fuel flow decreases. When the engine is not running the 
    fuel cannot get through to the carb.
    
    This design works well with inverted engines. Also the YS carb points
    downwards when inverted, The OS carb will be "Vent up" and can flood
    that way.
    
    Regards,
    
    Eric.

    My non-pumped OS91 Surpass runs great but I had some problems with it
    on the Panic.  Very violent manuvers sometimes cause the engine to
    quit.  I think this happens because of fuel pressure fluctuation due to
    fuel sloshing in the tank.  A 4-stroke doesn't have any reserve of fuel
    inside like a 2-stroke does.  (unless it's a YS)  I'm convinced that a
    pumped engine is the way to go for aerobatics.  It's the only way to
    keep from leaning out on verticals and to allow tank placement on the
    CG.
    
    Charlie
    

    Well, once again, the responses from these notes have helped me make a
    "better" decision.  I had originally purchased an OS 120 4 stroke for
    the Mustang, but as pointed out in several previous replys, this is not
    the engine of choice for an inverted in-cowl situation.  Eric and I
    talked off-line, and so I finally made up my mind to see if I could
    swap it for the YS120.
    
    To my surprise, RC Buyers agreed to take it back and ordered me the YS
    120 (without air chamber).  We reached an agreement to swap it at no
    change in price.  Even though the YS is a few dollars cheaper, I felt
    it was worth it since they don't stock 120 size engines, and they will
    be stuck with this one in inventory until a customer comes along.  I
    should have it by next week.
    
    Now I can put my mind at rest and get on with the building.
    
    Thanks again for all the help and advice.
    
    Regards,
    Joe
    
    PS: I suspect that an in-cowl mount such as the Mustang requires will
    cause me some headaches in terms of overheating unless I provide
    adequate air flow over the cyl head.  I know there's something in this
    notes file on cooling in-cowl jobs.  Does anyone remenber where it is? 
    Better still, has anyone got any tips for me?  

    Joe,
    	You want to duct air around the head and make sure you have plenty
    of exit area for the warm air.  You need at least 2X the exit area as
    the intake area because the warm air expands and takes more volume. 
    Run it without the cowl until you break it in and get it sorted out. 
    The exhaust gets very hot on these 4-strokers so don't run it too close
    to anything.
    
    Charlie
    

    I am having a problem getting my YS 120 started again.  I ran two tanks
    thru it last year, then put it on the shelf over the winter.  I now
    have it installed in the Goldberg Sukhoi.  Yesterday, I tried to start
    it but only managed to get any action by squirting fuel down the carb. 
    It would run for a few seconds, then die.  I repeated this procedure at
    different needle valve settings to no avail.  
    
    Then, after trying this about two dozen times without success, all of a 
    sudden it started running in a strange way, namely the
    speed would oscillate from high to low at a constant throttle setting,
    and moving the throttle stick had virtually no effect.  I tried turning
    the needle in, but this had no effect.  I then turned it out, and the
    engine finally started revving at full power, only to die several
    seconds later.  This was the longest run, lasting about a minute.
    
    Today I tried again, but everything was essentially a repeat of
    yesterday.  I did notice that when it was running, the line going from
    the carb to the nipple by the front bearing seemed to be bubbling, and
    the fuel appeared not to be flowing.  I know there is plenty of tank
    pressure because when I detach the fuel line from the tank, it squirts
    fuel at high pressure.
    
    Any thoughts about what could be wrong?  Might there be a blockage of
    gunk from laying around all winter?  If so, how do I find it?  I've
    never taken a 4 stroke apart before.   I tried blowing thru tubing
    connected to the various ports, but only the one going to the carb
    allowed the passage of air.  
    
    While I'm at it, let me ask how you apply after run oil to this engine. 
    I tried pumping it down all the ports, but they don't take it, so I
    took out the plug and squirted several drops into the cylinder head and
    cranked it over several dozen times.  
    
    Thanks for any help you can give.
    
    Regards,
    Joe 
                                                                     

    You say that the tank is pressurized because it squirts fuel when you
    pull it off the carb...  Did you by chance put a check valve in the
    line from exhaust to tank??  If not, then how is the tank maintaining
    pressure after the engine is shut down??
    
    How is the plumbing of the smoke system run??  Does that have a check
    valve??  It almost sounds like you have your fuel and smoke system
    plumbing crossed.
    
    However, with all of this pressure, I would think you are flooding the
    engine, in which case priming would not help (which from your note it
    apparently does..)  So I would still suspect a carb problem.
    
    How does the choke work on that engine??  On the Enya 120, the carb
    barrel is actually moved to one side..  Might the carb be in the
    choked position??  (Again, I doubt this as it would lead to flooding.
    
    If you want to avoid pulling everything, try running the engine from
    an external tank with fresh plumbing..  If it runs, the problem is the
    plumbing, if it doesn't, then it is the carb.
    
    Good luck!
    jeff
    

    
    
         Joe,
    
            What Jeff says makes sense, isolate the engine from the
    plumbing and see if the problem is in the plumbing. If its not, the
    regulator is usually the next place to check for trouble. 
    
    A couple of things to consider regarding YS engines:
    
          You should be running a check valve in the pump output line. This
    does two things, it prevents any fuel from backing up into the
    engine pump and holds the pressure in the tank, second it allows you 
    to remove the pressure from the tank before refueling. 
        All the pattern planes have fittings which route both the input and 
    output lines ( via fittings ) outside the fuselage and then back into 
    the fuselage. The check valve is installed in the portion outside the 
    fuselage. The process is to disconnect the check valve which relieves
    the tank pressure, THEN disconnect the line going back to the engine
    and refuel. 
    
         Another consideration is that many "after run" oils will attack
    the silicone gaskets in a YS engine. For this reason, a lot of flyers
    including Eric Henderson, Charlie Watt, Dan Snow, etc have been using
    Mobil 1 exlusively as their afterrun oil in YS engines. It is a
    possibility that if the engine ran fine last fall and then you put 
    after run oil in it for the winter that the oil has wrecked the seals.
    
         As I mentioned to you, I have forwarded your problem to Charlie
    Watt, so maybe he will have an idea what the problem is.
    
                                                            Dan
        

    Jeff, there is a check valve in the line coming from the pressure tap
    and it does indeed keep the tank pressurized for a long time.  So that
    seems to be OK.
    
    The smoker is a pump unit, so the only point where it comes in contact
    with the engine system is the inlet tube on the muffler which sprays
    the fluid into the hot exhaust gas.  Doesn't appear like this is the
    problem.
    
    Choke??  Didn't know I had one.  I see the carb and inside it has a
    butterfly valve that rotates with the throttle linkage.  This appears
    to be the throttle, but it sure looks like a choke.
    
    I'll be at the Merrimack field tonite for training, and if you're there
    we can discuss more.
    
    Regards,
    Joe

    Just read Dan's reply.
    
    Last fall I put some petroleum-based after run oil in before I knew
    there was a problem with it attacking the membrane.  So its entirely
    possible this is the problem.  How do I replace it?  
    
    Re: bringing both lines outside the fuse for reducing pressure and
    filling.  UGH!!  It will ruin my nice clean cowl.  Bummer.
    
    -Joe

    Joe... call me at 445-6577; I have a YS 120.
    
    Also, the previous recommendations to try an external tank for
    troubleshooting is a very good suggestion.  I have used this technique
    many times to isolate problems to the fuel system or engine.
    
    Chris
    

    
    
       Joe,
                                                 
          You don't HAVE to route the fuel lines outside the fuselage, It 
    just makes it much easier to refuel. I agree its ugly, but the 
    convienence more than makes up for the looks.  In any case, you need 
    to be able to relieve the pressure via the check valve or you will 
    shoot fuel several feet when disconnecting the fuel line for refueling.
    The check valve also needs to be disconnected to allow the air to 
    flow out of the tank when you pump fuel into the tank during refueling.
    
         Re: Silicone
    
        The diaphram in the regulator is made of silicone and is one
    of the pieces prone to damage. If this is the problem, you will need 
    to order one of these (buy a few) from your friendly YS dealer. I am 
    not sure what other silicone pieces are in the pump of a  YS 1.20. I 
    think the gaskets will be fine, but they aren't that expensive, so
    I would suggest ordering at least a spare regulator and carb gasket
    at the same time.