I just got my second OS 70 FL 4 stroke. Not because I'm cheap, or don't know any better, but because it only weighs 1.1 ounces more than a .46AX. Anyways, it has the typical ABC squeek, only on a 4 stroke, it's more noticable at TDC on a non compressed stroke. I've broken it in on the bench, and I've burned 2 tanks on the ground, and 1 in the air, and still sounds like an old chevy with a stuck lifter. My question is when will the squeek go away? Or will it?

Might be a long time. I've flown engines for a 100 flights and they still had the squeek when cold.

When the sleeve are hot and will be expanded, the squeek will disappeared , nothing to be worried.

Jens Eirik

Gordon,


ABC and ABN engines are never supposed to completely lose their cold pinch.

As Dub Jett wrote in his web site, when ABC type engines finally do lose their pinch, they are worn out.


As Jens wrote, when they are running, the differential expansion of the sleeve, with the engine at its normal working temperature, causes the pinch to disappear.