All

My guess is pull mag side cover remove flywheel and replace crank seal.im betting problem goes away, cheap easy to do and good insrance.

What carb is on it and has it been bored/taper bored?

I suspect a air leak. Plug your exhaust and intake opening and do a leak down test. See if it will hold 6 lbs of air/pressure. You can find the leaks with a spray bottle with water/soap.

Bottom line is you need around a 9.5:1 compression ratio with about a 60% squish band and ext port timing around 180° with a 28-30° blowdown phase and a good low_mid range pipe with two stage reeds. You put that combo together and you will have the bottom end your looking for.

Bottom line is you need around a 9.5:1 compression ratio with about a 60% squish band and ext port timing around 180° with a 28-30° blowdown phase and a good low_mid range pipe with two stage reeds. You put that combo together and you will have the bottom end your looking for.

Cutting the head reducing the cc will raise compression and will deliver more power/response. If your goal is to change the powerband and add more bottom end, reducing the cc isn't they way to accomplish it. The shape of the cumbustion chamber and the squish band width and break area will have some effect on the powerband. Port timing and...