Ed it sounds like the majority will interfere, the op has one with excessive squish from the start! I am guessing the base gasket is .015 like the 661. Stihl’s factory squish can be all over the board, I have a stock 660 that has .019 squish with gasket, also have an odd ms260 that had excessive squish and I could do a base gasket delete, the ms260 is not supposed to be able to bgd either. Ms 461 I have seen about.007 difference in several jugs and 660 have seen .016 different between different factory jugs.I thought I saw something about interference when deleting the base gasket on these … am I wrong???
Ya do that, the piston rocks when you check above the exhaust or intake and give a false reading, I had a 461 the would turn over with a base gasket delete because of carbon build up, de-carbon the chamber and .016 squish, sanded out .002 from the chamber with an old piston and stick on sandpaper@Bigmac Yeah that's what I was thinking. By the time I clean everything up I'll probably get my .002 back. I did check above the exhaust, I see what you're saying. It hadn't occurred to me to check over the wrist pin. I'll clean it all up torque it down and recheck.
So what’s your max on a 70cc saw?.018 is plenty, that’s what my 066 was stock.
I do know of numerous 120cc work saws built with .015 and never an issue.
stihl ultra is not your friend