I have a OS 91 Surpass on a Stick which runs like a top. The only problem and it may not even be a problem is that when you cut the throttle the engine seems to take a little time to reach full idle....like maybe 10 or 15 seconds.....not sure what the problem is because it idles fine....just takes a little time to get there....ANYONE HAVE ANY IDEAS???

If the engine takes a while to idle down, it's usually because the idle mixture's a bit on the rich side. When you lean it a hair, you may have to up the idle RPM a hair to compensate.

Question: I have a OS FS-91 Surpass ,when I can get it to idle it sounds like it has pre ignition you can feel it through the plane, also when we got it to run, it use a large amount of fuel in a very very short time, (up for 5min and burnt a tank of fuel and smoked like it had a smoker on it). I obtained the engine w/plane and was advised that the o-ring in the needle valve had been replaced (if its the right one know one can tell me) also when we ran it and it was using all the fuel the needle valve was all but closed, we had it opened 1/4 turn from closed on the first and last flight until we solve the problems.
getting parts is hard were I am at so where would one start, I have thought about just replacing the carb but can not find one that matches the part numbers (45981000) in my manual and the manual does not give a model number for the carb.