I had GPM in my Egli when it was !000. There was an article by Neville Higgins in MPH many years ago explaining that they are good pistons but as Bill says they are round. You need to relieve the skirts at the four points close to the cylinder studs with a fine file and they will be fine. Mine did many thousand miles without a problem.Anyway, continuing the thread. I have now stripped the top end. The bore looks absolutely fine and the piston will be OK with a bit of a clean up. As I thought the nip up area on the worst part just seemed to be catching the oil ring. I measured the oil hole in the liner and the top of the hole is a good 3-4mm BELOW the bottom edge of the oil ring so I am assuming this is also fine. I have yet to strip and check the cylinder head but will do that next.
Can anyone identify the piston please as I might want to change the rings?
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Cheers Bill