Re: 42 miles of He.....
Junked, my skyhawk was doing similar to yours at the beginning of the year (around its 500th mile) I was stumped on how to fix it as well. I rode across town probably about 10 miles and on my way home the motor would not rev fully, and at every stop light it 4 stroked like crazy. My top speed went from 32MPH to 18MPH, and it began leaking oil from the magneto case. I went home checked my seals on the head, replaced the bottom jug gasket and head gasket, exhaust and intake gasket. Cleaned the carb, and even checked all of my wiring. After nearly a full day of work I test rode it, same thing it ran horribly barely pulled me. I went back in the shop and thought it could be clogged catalytic converter. I only thought of this because my impala the same week had a bad catalytic converter, it only drove 20MPH tops for 3 days before I took it to the shop. Anyways I drilled a hole in the tip of the muffler to bypass the catalytic converter, and went for a test ride. It was a bit louder but it ran like a brand new engine I was very surprised. Just make sure you have or know somebody that has a welder you can plug the hole up with if this does not fix your problem. Good luck!