I have an 84 200es which i bought new back then. She got tired, so last winter I had her bored out 50 over; new piston, rings, timing chain, valves, seals, pulser, cdi, coil, carb,.On the bench,she had 150psi. After i put the engine in the frame it had 130psi. Timing and valve clearances are right. At low rpm she has lots of torque, but as the revs. come up she loses power. She wont go up a grade on the road without getting back into low range and 1st. or 2nd. gear. She used to carry me and my lady along easily in 4th and 5th in the high range. I still need the bike to service food plots for deer in my place plus other chores. I really am stumped. The worst is that i build engines for bent toys!!! Thank You .

 

replace the cdi unit

hondas brain fart of an idea by mounting the coil and cdi overtop of the engine

being cooked by the engine heat

 

should have read your post more clearly
you bored the cylinder 50 thous over ( way too much over bore )

on air cooled atv engines , you should only bore the cylinder 1 size larger from what the worn out cylinder measured

now you must re-jet your carb to compensate for the now larger combustion chamber

 

I would have to re check the valve timing. It sounds slow or retarded to me.