Hello all, I have a os 91 fx with about 3 hours on it. I have had a problem with the low end of this motor from the beginning. Top in runs great and it starts very good but when you set the low end needle it runs rough at idle and even misses. Up about half throttle it has a gurgleing sound. I even had a friend that is pretty good at setting carbs and he couldn't get it set either. Any ideas ?.All help will be greatly appreciated. Keep them flying.

this engine is like any other glow motor, peak the Hi then richen 300rpm, them set low for best transition and idle. If it still won't run correctly something else is wrong. Have you up dated with the new remote needle valve OS is selling? This is a strong engine if set up correctly.

There are two in my club in identical Cermark Sukhois, the original one. Both with a Pitts style muffler, engine mounted sideways. Both run great on 10% fuel. The other guy tried 15%, had all kinds of problems. Switched to 10% and had much better luck. Mine's always been run on 10%. It took a while with tiny adjustments, but now both engines idle, transition and run great.

Excellent engines, perfect for these aerobats. We run 14X6 props, usually. Lately he's been hovering with a different plane, and is talking about using a 15X4. We tried the recommended 13 X 8, makes it difficult to land, but it spools up instantly. The 15X6 I tried was slow spooling up, but provided excellent braking on approach. The 14 X 6 is a compromise, good acceleration, and a little braking on approach.

Try a different muffler, or different fuel, or prop or something.

Thanks guys I will give your ideas a try. Great flying

Edge:

There have been many posts about problems with the 91FX. Do a search, you'll see how others have gotten them to run acceptably.

Bill.

Edge,


Do a search in RC Universe for information on this engine.

There are several threads, in which modelers stated quite severe problems they were experiencing with it.
In some of the threads there are suggested solutions.

It is also possible OS has admitted to there having been problems and rectified them with FREE replacement of parts.


None of those that started these threads has taken the trouble to reply (yet).

This engine is not like any other glow motor. It is the lemon of the OS line up and has been since the day it came out. I returned two of them within a month about 3-4 years ago. It 's not worth wasting your time with.

This engine is fantastic, as long as you dont get one of the lemons (which seems to me to be about 40%). Mine certainly runs well once solved. Incidentally I have just bought the C-Spec upgrade from Tower Hobbies, which will also eliminate the problem, though then it is starting to get expensive.