Was just going to get my teeth into this [most teeth mithing] but see i've rambled on back a page so i'll just re-run it as pretty much covers my thoughts. loved the one i rode when new or almost new--must have a pic somewhere, front wheel in the air passing my boss on his yz360b mono up a track. Hope ya get it sorted. Not reed valve so can't have piston back to front--well can but not the problem. Someone [apprentice] not made a base gasket for you & omitted to cut out for the transfers?, don't laugh i've seen it happen, ran but only just. Ok, wifey's home--yes dear i've been busy!!--panic. Just reinforce cleaning the exhaust & if in doubt then cut it open or at least slide a garden hose or something down the tail pipe to be sure she aint restricted at the weld where tail pipe joins. Plus be sure of muffler internals. Got caught out once on a GoKart which went like hell i thought but not compared to another identical Racket motor or something with a vacuum power valve & muffler was collapsing inside & partialy blocking the pipe.
If it starts & runs [i think] the problem lies elsewhere. CDI spark never looks 'that healthy' but would make ya hair stand on end--or fall out. No chance of something 'accidentally' left under the seat restricting air cleaner air flow. Sounds like restricted exhaust as another option, or main jet fell out or slide needle still sitting on the bench. Sorry if that sounds a bit off but more or less just letting the cat out of the bag to all the cock ups i've made over the years lol. & just when i think i've covered the field of cock ups i go & 'discover' a new one. If it's definitely electrically missing its bum off then ok--i give in & ignore all my rambling. Just tend to think if it starts--it's ok--unless they have a high speed winding separate from the initial source coil but think you said swapped stators so that ideas out the window. Cheers [or tears]. ps, i road one of those for a few meets back when new & was a very enjoyable time too--well till a rear brake shoe spring broke & locked the wheel miles from the finish of a long distance race. Very willing motor.
