P.S What is the typical compression test reading on these small engines? I just modified a compression tester to work and tryed a few tests. The string trimmers, 25-31cc seem to all test out at 85-95 psi. The ones that feel they have good compression are only slightly better than the ones that feel to have poor compression. These cheap lawn care motors rarely have 2 rings, the ones I checked were all one ring engines. I looked at chain saw repair videos on line, and they seem to all consider 150psi to be a good test, but these are all multi ring engines. I am tempted to try adding another ring using my small lathe, but I suspect the vibration will be a problem.