Originally Posted by
drac1
These are standard heat treated spring steel internal circlips. If you have tried to destroy one, (I have), you would know they are virtually indestructible. These circlips are not designed to have force exerted on them and in this situation there would be very little. I am also extremely doubtful that they would fail due to vibration. It would be more plausible to think that the groove in the piston would be the problem, but even then it doesn't make sense to me as there would be minimal pressure applied to the circlip.
Obviously there is a problem somewhere and it would be very interesting to know exactly what it is. It's more than likely we'll never know the real issue.
I was given a Stihl chainsaw that had compression but the cylinder was cored. Cause.... The wrist pin circlip broke. It was a single tang clip. The other good side broke as i was removing it. I've also seen this happen in some of the .15 racing engines we used in Quarter Midget of years past. Many possibilities... Wrong temper of the material, bending past the yield point of the material or any combination of factors.
My guess is a bad batch of clips snuck through QC and they will run their course and all will be happy again.
Ken