I just dusted off my old 1985 YZ80 and spun a few laps in the back yard. Wow the memories! I think I'll bring it to the track next time out and run some laps with the kids just for kicks. Here's the problem. It's got an .06 oversized piston, boynsen dual stage reeds, a PSI pipe (very peaky, top end only) with an FMF silencer. It will idle as smooth as my 426 all day long, runs perfectly smooth on bottom. If I open the throttle from idle, it will pull hard right out to about 50% of the RPM that it's good for, where suddenly it hits a flat spot where it just about completely stops making power, then a couple thousand RPM later suddenly it jumps on the pipe and pulls as hard as an antique 80cc bike can pull. So the question is, what's up with the flat spot. It has been that way for as long as I can remember (even when I was a kid), a jetting issue I assume. I assume my main jet may be a little too small but I wanted to double check with the old 2-stroke crowd before I buy parts and head out to the track.