My faithful 1.60 suddenly started having idle surging issues and it won't shut down now with the throttle trim. It has been rock solid since day one.

Fuel is the same fuel I've been running since day one, I did try a different bottle from another batch and the fuel runs fine in my other engines. Scratch a fuel issue.

The Top end went away today and the normally reliable idle is kaka. It sure sounds like a air leak somewhere but dang if I can find one. The Valves are still adjusted correctly and the fuel system is sealed. I don't see any fuel leaks on the engine. Valve cover is flat and sealing.

821 muffler, Cool Power 30% Heli, 17-12 Prop. I don't feel bad bearings and it actually starts easily. There is a contest I want to go to this coming weekend but not with this problem.

Anyone?

Tim

Tim,

About how many flights do you have in this engine? Just a ball park. A couple guys I know said they saw top end power drop off and the idle start to be a problem when the ring got worn.

Maybe 100, Comp feels good, a worn ring wouldn't explain the can't shut it off. If my other 1.60 runs ok I'm going to swap them out and see if it's in the engine. I believe it is.

This was a sudden problem. One flight to the next. Thinking about it the last good flight I did hear it sag once in a vertical. It was the last flight of the day so I didn't think anything of it.

The most common cause of a air leak is from the O rings on the push rod tubes, they can dislodge from a simple backfire,
have a good look at them , if one part is protuding futher out than the rest, there is your problem.
But sometimes you can't see the damaged O ring untill the engine is disasembled.

Did you check the rocker cover gasket, or, I know I did the refacing but havn't checked it.

Check these first before you go any futher.

YS Service Down Under

Tim,

Check the small fuel line from the crank case up to the pump. If that gets the smallest pin hole in it, you'll see some of those exact symptoms.

Arch

Thanks Arch, I'll check it tonight. You going to be at Buff's? I want to try and make it down Friday if I can get this fixed for some practice.

Tim,

That is the plan. I'll leave here REALLY early Friday morning, getting there around noon.

Arch

Well I fixed it, What I found was a cut O ring on the upper exhaust push rod tube. Popped new O rings in her and test ran it and my baby is back to normal. I had to look at it with a strong light and a mirror to see it.

Tim,

Glad to hear it. See you Friday.

Arch