All the ones that I have messed with would burn up at about 15 hours due to crank seals leaking around the cases. I have seen 3 different ones die from failed crank seals, One of those got a new crank twice. A friend of mine tried to convince me they could be better then a banshee if all the weak points were addressed. He also said in 88 or 89 they changed to a better frame with a power valve motor. P.S it sucked too.
Your bike needs inspected. Check the jetting and compression test. It may be jetted for a different temp or altitude.
Learn how to read your plugs. passion racing.com has spark plug reading tips with picture.http://www.passionracingengines.com/files/plugchart11.png
Yeah, all you need to do is hog out the intake really big right?? I would drill holes all the way through the transfers and to the out side of the cylinder and add extra ports. You could use pvc or something. Who wants the first 20 port design?
duel pingle, fmfs and cub... Maybe someone couldn't let go of their drag pipes when they sold it. You need some cpi or shear drag pipes,I want to try some rockets.Also that stock swinger will not work once you dicth the fmfs.
On the outside of the cylinder their should be a 10 mm bolt to drain the coolant, If it has that it is more then likely a stock cylinder. Also cubs are mono block meaning 1 piece. stock cylinders separate, meaning they are 2 individual pieces.