Home › Forum › Ask A Member › 18 HP fastwin on E-bay › Re: 18 HP fastwin on E-bay
Well, some of what you mentioned affects the compression. Some not.
To get anal here, there is cylinder compression (what we mainly talk about), and crankcase compression(hard to measure, so rarely talked about).
Cylinder compression is affected by the bore first and foremost. IE, is the bore worn oversize, gouges in the cylinder wall, out of round, etc…
Then other factors come into play, such as piston ring condition, if a ring is stuck, piston condition (gouges, etc…), the "trueness" of the head and block, and the condition of the head gasket. Those are the main contributing factors which would affect cylinder compression. Some motors, with components like compression relief valves could come into play, but will try to keep this general.
Then there is crankcase compression. Equally as important, but harder to measure, so rarely talked about. Many motors I have seen, that cannot get made to run, suffer from crankcase leaks. As stated, sometimes hard to evaluate, so when the owner has gone through everything else, and still cannot get a motor to run right, it is just put aside as a parts motor. Again, hard to generalize all motors here, but trying to KISS (keep it simple)