Dave,

I sent this engine in and you guys checked it out last year and said it was fine. It seemed to run much
better when I got it back.

However all along I did notice some engine surging with the Futaba GV-1 governor engaged but it was slight.

Now the engine surges all buy itself without the governor engaged....and gets really bad with the governor on. So bad
that I can't fly it.

Any ideas what to check for??? What would cause the engine to not keep a consistent speed? Needle valve adjustments are
right in the ballpark of what the manual shows. Tank pressure is there. New glowplug, rear bearing, conn rod.

Thanks for your help in advance!

Michael

Surging indicates varying fuel or pressure supply. Have you checked all the engine bolts to make sure none are loose?
How much time on the engine since you got it back from us?

Dave,

I would estimate about 12 to 20 runs on the engine since I received it back from you. I ended up putting in a new rear bearing
during the winter because of some slight corrosion.

I have tried alot of things. Just last night I completely dissassembled the carb and put everything in alcohol and even blew
air thru the openings. The regulator seemed to be working...and I didn't see anything unusual. However today I again tried it out
and still it is not running consistent especially when I give it collective/throttle. It seems to at first run lean and then rich again and adjusting the needles doesn't seem to do much good. This is all without the Futaba GV-1 turned on.

I will put my other YS 61ST-2 on it and try it out just to prove it is the engine.

Could it be possible that the carb tolerances are just worn to the point where the engine will not run correctly at mid and high throttle?
The engine idles fine and even hovers fairly well ...it is just when I give it more collective/throttle that causes the problem (high end seems lean and then when you go back to hover it gets rich....then the surgine starts).

Any more ideas because I have run out of them? Also could I run it on the bench with a prop...if so what size and what rpms should I expect?

Also what about the diaghram. I notice that I can turn the inner black piece free from the clear rubber. Could pressure be leaking from
this at higher fuel pressure???

Thanks for your help,

Michael

It's not likely that you could tell anything running on a prop, but it might be worth a try. The regulator is probably the culprit in this and there is almost no way to repair them, they usually have to be replaced when they go haywire.

Dave,

Is there more to checking out the regulator then just blowing into
one end while operating the valve by hand? If I push the valve
down it lets air thru. Let it go it stops the flow. Also the air is
going into the area where the diaghram is and not out the other
nipple? What is the other nipple for?

Are there any articles on how YS's system works?

Thank you,

Michael

No articles that I know of. It's a demand type regulator that operates on crankcase pressure vs. throttle position. The regulator can give up at any time without warning, sometimes lasting the life of the engine, other times not. But for the most part they tend to live a long time in a vary harsh environment.

Dave,

Today I had a chance to try a different known good regulator assembly on my YS61ST2 engine. It is not the regulator....the engine ran just as bad with it. I also had the opportunity to put the good reg on my other YS61ST2 (the one where it came from) and remount it in the heli and the engine ran fine...with or without the governor engaged. So that leaves the carb and piston/sleeve as the problem area...and those parts are very expensive and I feel it is just better to buy a new engine as this point.

The engine just does not run consistent.....leaning out when I give throttle/collective and then when you go back to hover it surges back and forth.

Thanks for your help... I guess the engine just has too much time on it?

Michael

Give me a call at 775-265-7523 on Monday. We can work out a replacement engine for you if you prefer.

Dave