What would be the minimum compression to start ms171 chainsaw. Story is I acquired above saw, compression was very low and found stuck piston ring (piston seemed in good shape ie noscoring etc). Replaced ring and compression went to 90 psi, saw wouldn't start so cleaned carb etc still won't start, put a bit of carb cleaner down plug but still wouldn't start, checked spark plug all good, still wouldn't start so now I'm thinking if compression is just too low and maybe needs new cylinder, piston etc. What would your opinion be. Thankyou