I've had this YS .91AC for over 10 years in a Goldberg Extra (several of those years just sitting). It had been running ok, but down on power slightly, I thought. Anyway I flew it the other day and it ran fine (except I did have to speed up the idle slightly from normal), then for the 2nd flight of the day would barely start and would keep dying. Now it won't start at idle and it may run at 1/2 or full throttle for a while, but will run slightly erratic. Once I throttle down it dies. One odd thing, there is fuel dripping from around the throttle arm.

I went back and changed all the settings to stock (high speed, low speed and pump) with no luck (running new Powermaster 20/20 fuel, YS glow plug and APC 15x8 prop).

I checked the valves and they are ok, changed the glow plug, changed the check valve. I took it out of the plane and checked all bolts, they were tight. It has pressure when I unhook the check valve, so don't see the tank as being an issue. I also changed the fuel lines on the engine. All of this with no help.

((2 days later))
Well, I ordered replacement gaskets and a diaphragm and installed them, but no luck. It will run better than before, so 1/4 throttle to full throttle runs fairly well. Once you get down around 2,000-2,500 rpm it will idle for anywhere from 0-15 seconds, then die. About ready to toss it and get a 1.10 (plus the .91 just doesn't have the umph to pull a Goldberg Extra). (The 15x8 APC only turns around 8,300)

Guess the bearing are the next thing to checck, but just not sure it is worth all this aggrevation.

Any thoughts?