Conference vmszoo::rc

        Re:< Note 294.0 by 29930::FISHER "Battery, Mags, & Gas Off!" >

        Kay,
        
                My low  spped  mixture  screw turns just like yours, hard
        and rubbery.   The  engine  is installed without a pump, but with
        the fuel tank at the right height.
        
                The  adjustment  procedure  I  use  (don't  remember  the
        instructions in the booklet) is:    Adjust the high speed mixture
        until the engine runs well at full throttle.  Then back off until
        the engine starts running rough.  Adjust  the  low  speed mixture
        until it runs smoothly and back off a bit on the throttle.  Then,
        and  this is important, readjust the high speed mixture  at  full
        throttle again and repeat all over again until you have both good
        low spped and high speed performance.
        
                Bill's and my engines rev just under 10K with 11x6 props.
        
        Anker

        Re:< Note 294.0 by 29930::FISHER "Battery, Mags, & Gas Off!" >

        Kay,
        
                I just  had  a  thought.   Did you remember to adjust the
        valve clearance after  running  the  engine  in?  I did and found
        that they did need adjustments.  Your problems could be caused by
        not enough clearance.  Also, how is the compression.  Both Bill's
        and my engines have extremely good  compression.  If you don't it
        could be the oppsite problem, burnt valve seats!
        
        Anker

>                I just  had  a  thought.   Did you remember to adjust the
>        valve clearance after  running  the  engine  in?  I did and found
>        that they did need adjustments.  Your problems could be caused by

I checked it this weekend - they were loose but setting correct didn't change
performance.

>        not enough clearance.  Also, how is the compression.  Both Bill's
>        and my engines have extremely good  compression.  If you don't it
>        could be the oppsite problem, burnt valve seats!

I thought about compression a lot and couldn't figure out a clever way
(Al Casey are you listening) to check compression.  I thought there must
be some way with a tire gage that you could check but I'll leave that as
an exercise for this notes file to figure out.  Now suppose I could test it
what should it be?  Anyway I pulled the glow plug and felt the compression
with my finger.  If I tried hard I could hold it back without it leaking
so I concluded it was good.

Then I figured that maybe my fuel was bad - It has been setting in a garage
in a fuel can in the flight box with the pump lines still installed (not a 
great seal).  So I tried new fuel.  Thought I was getting somewhere cause as
soon as I switched I couldn't start the engine.  I figured if it was that
different then the old fuel must have been bad.  Unfortunately after I got
it running it acted the same again (tho with different needle adjustments).

Then I got to looking at the prop closer.  It didn't seem to be tracking too
true.  Looked fine running but when I turned it by hand it looked funny.
So I went to swap it for another 11x6 and when I took it off I discovered that
it was a 11x7.  Gad!  Swapped to a real 11x6 and I could then get 9,500
leaned out.  

So then I readjusted and put the old fuel back in and it didn't require
any readjustment and ran fine.

The next test will be at the flight line.

              _!_      
Bye        ----O----   
Kay R. Fisher / \     

================================================================================

    Kay,
    
    I know of no method or gauge (commercial or home-brew) for testing/
    checking model engine compression.  I suppose some gadgeteer could
    adapt a bored-out glo-plug to an automotive-type gauge but, as you've
    already questioned, what would be a "normal/acceptable" reading?...
    and how would you check it?...turn the engine over by hand...with
    a starter???  I dunno' fer' sure and I don't believe I've ever seen
    compression spec's from a manufacturer so I'm not sure of what value
    this information might be except, perhaps, for making occasional
    "relative" checks.
    
    Adios,	Al

        Re:< Note 294.4 by GHANI::CASEYA "THE DESERT RAT RC-AV8R" >

                I use  the  crude  method.    If  I can feel that there's
        compression when turning  over  by  hand  it's good.  Remember to
        have the throttle open!    An  engine  with  bad compression just
        turns happily over without any  noticable  resistance.  An engine
        with  super  compression  turns tightly through  the  compression
        point and then spins right through and  cuts the finger pushed it
        with.
        
                I  spent most of Sunday practicing what I  preached.    I
        learned  that  on  my  Saito  you  shouldn't use the  compression
        fitting  on  the exhaust.  The engine is only adjustable  without
        compression on the fuel tank. It finally ran just beautifully.
        
                I'm glad you found your problem. You'll love that Saito!
        
        Anker

re Note 294.5 by MURPHY::ANKER "Anker Berg-Sonne" 
...
>                I  spent most of Sunday practicing what I  preached.    I
>        learned  that  on  my  Saito  you  shouldn't use the  compression
>        fitting  on  the exhaust.  The engine is only adjustable  without
>        compression on the fuel tank. It finally ran just beautifully.

OK - suppose I decide to leave off the muffler pressure.  What do I do with
the line to the fuel tank?  I would suppose it dumps fuel during every
roll if I leave it open.  I would suppose it would starve the engine
if I close it.

First assume that I'm not willing to redo the tank to be a vented tank.

How can you love an engine that won't run on the exhaust pressure fitting
that they supply for that purpose?  I'm beginning to believe Al Casey.
These four strokes have a high fiddle to fun ratio.  I was running a
OS .60 FS to days ago that I bought used thru this notes file.  Same
crap - I fiddled for a half hour then it started running right.  Probably
ended up with the same adjustments that it started at.  It doesn't make
since to me that an engine the size of these should have to warm up for
half an hour.

              _!_      
Bye        ----O----   
Kay R. Fisher / \     

================================================================================

    How about a check valve in the vent line if you run with no muffler
    pressure?  It would let air in, but would keep fuel from dumping
    when inverted.
    
    Or, if running with pressure, can you decrease the pressure by
    restricting the line with say the appropriate size wheel collar
    tightened down on the tubing to some magic point?
    
    Just some food for thought,
    Chris

re Note 294.7 by MDVAX1::SPOHR 

>    How about a check valve in the vent line if you run with no muffler
>    pressure?  It would let air in, but would keep fuel from dumping
>    when inverted.
    
Do they make such an animal that will fit our little fuel lines?

              _!_      
Bye        ----O----   
Kay R. Fisher / \     

================================================================================

    Kay,
    
    Look in the Sept. issue of RCM.  Near the very front is an article
    on smoke systems.  Both of the methods I mentioned were in that
    article for the purpose of regulating a smoke system.  I think it
    would work in a similar manner for you.  As to where to get them,
    you got me.  Since they talk about em there, try checking the article.
    I would check for you, but this is the last time I will be in notes
    until next Thursday (DECworld you know).
    
    Good luck,
    Chris
    

        Re:< Note 294.6 by TALLIS::FISHER "Battery, Mags, & Gas Off!" >

>OK - suppose I decide to leave off the muffler pressure.  What do I do with
>the line to the fuel tank?  I would suppose it dumps fuel during every
>roll if I leave it open.  I would suppose it would starve the engine
>if I close it.
        
                Run the  vent line out below the engine.  Right side up -
        the line in  the  tank is above the fuel line.  Upside down - the
        end of the vent  line is above the fuel tank.  Result - no leaks.
        In any case there is  always  fuel  running out of the tank (into
        the carb) so it shouldn't dump fuel no matter where the vent line
        runs.

        Anker