YS 91 AC problem

[Ihncheol Park]

Paul,
sorry to hear about the problem.
For correct part name check the link.
http://www.centralhobbies.com/Engines/parts/YS91ACEX.html

I believe small amount of tiny bubble between the regulator and carb during
idle is normal.
If you have a lot of bubble or didnot have bubble prior to the crash, check
the regulator assembly.  Get a small magnifier to look at the diaphragm for
any crack.

Are you talking about the throttle stop screw?
  "The idle adjust scred broke off and with help it has been removed, I am
now
running without the set scred."

If you don't have the throttle stop screw, the throttle barrel may move in
and out slightly although there is a seal on it.  It get torn easily if the
throttle barrel is not inserted smoothly. (I tore a few when I install
throttle barrel)  The center of the throttle barrel has tiny slot (I do not
mean the the hole).
This may cause idle problem.

I suggest you to check the throttle barrel (including the idle adjustment
needle valve removed) and carb for any blockage.

I am sure you cleaned up inside the engine just to make sure nothing went
through the carb.  Right?

After checking all the above, reset the valve clearance, then, try again.
Hope this helps,

Ihncheol Park



-----Original Message-----
From: discussion-request at nsrca.org
[mailto:discussion-request at nsrca.org]On Behalf Of Paul Horan
Sent: Thursday, May 15, 2003 5:14 PM
To: discussion at nsrca.org
Subject: YS 91 AC problem


    During the Waco contest my Meridian/YS91 died on take-off, messed up the
belly pan and broke the Hyde mount.  With Wayne's help the belly pan is OK
but the engine has an idle problem.  The top end is good 8500 on a 14x10.
The idle adjust scred broke off and with help it has been removed, I am now
running without the set scred.  I also had an air leak around the intake
lifter tube and this has been corrected.
    Now the engine idles at approx 2500 but I cannot get it below that even
if I completely close the butterfly; also, the idle mixture screw has no
effect !  I notice air bubbles between the pump body and the carb when
idling, no bubbles in the tank side and there are no bubbles at mid to high
throttle.  Only at idle.
    Any ideas ?
Thanks,
Paul

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