Hi Dave, I have a YS 110 that is about 2 years old. When I first got it, I ran it on the bench for 2 gallons of Cool Power 15% Heli.(outside temperature was 55 degrees) I took my time running it very rich with an occasional leaner setting. The engine seemed to run fine and installed it on the plane. I flew it about 5 times and it was o.k. at first but then started to surge at around 2700 rpms (this is the idle up setting on my transmitter). It would loose rpms until it would almost quit then surge up to around 2700rpm. This would be continuos until I throttled up. Not much fun for setting up approaches and landing. Well since I had other planes/engines I just put it away last year and didn't mess with it. Now I want to get it straightened out and after reading some posts about possible plunger problems, I'm not sure if I should try twisting and adjusting things or not. What do you suggest? Thanks Ben p.s( I switched to 20% Cool Power pro pattern fuel while flying)

First of all, get the right fuel. YS 20/20 or 30% heli fuel.

Then go to www.ysperformance.com and follow the setup instructions. I think you'll get it sorted out OK.

Let me know.

Dave, You said I need to get the right fuel. I thought I had it right. Cool Power 20% Pro Pattern is 20% nitro and 20% synthetic. Isn't that the same blend as YS 20/20? Am I missing something? Thanks again Ben

Sorry, I missed it in the first post. That's what I get for doing anything late on Friday.

The fuel is fine. Try going through setup again, and if you can't get it sorted out, call our service dept. and have Richard send you a new plunger assembly.

Dave I got a similar, rather, identical problem. I hadn't run my engine in a few or so weeks prior to running it today. It is brand new and The last time I ran it I deadsticked it because I am running way rich still.
Anyway, I attempted to solve the idle problem by opening up the air bleed (idle needle). However, right a way, the engine seemed to be at a very high idle from the last time I checked it, then started dropping and surging, I ran it to full power and tuned the high end a little better and let it warm up. I brang it back to idle and brang the idle speed down a bit and it immediately died. It dies almost as if running out of fuel, but it starts back up immediately and easily, then surges, drops rpw to what one would think to be a stable, slow idle, then it surges and dies. I messed with different low end needle settings for an hour to no success. Is this a diaphram/plunger problem? is it possible that some fuel had gelled up in it and damaged it? Also, I am at 7000 feet asl - would that require me to adjust the regulator? BTW, I am running magnum 30% heli...

Try going to the setup instructions at www.ysperformance.com If that doesn't do it, I would suggest sending the engine to our service dept for a look, or possibly replacing the plunger yourself.