Weak powerband... Jetting???????

You seem to have answered your own question.

Make sure any mechanical issues are straight first, like piston, rings & seals.. Make sure the carb is clean and the float valve is in good shape.

Then jet it properly.

You'll see a world of difference if everything is in spec and the bike is jetted proper.

It might be a good starting point.

You need to make sure that all the mechanicals are in order, then get a baseline for your jetting, whether it be Pro Circuit or STOCK, and do the plug chops and that sort of thing.

You could probably line up 5 bikes with the same issues and the same jets and get 5 different results. There are so many factors that go into a properly jetted bike, that you can't just go with one set standard and be perfect.

It's trial and error..

Then you have to factor in things like temperature, fuel quality, how you ride.. crap like that that no one can ever quite nail down.

Good thing to do is get it as close as you can to running perfect, and have a couple sizes both ways on your pilot and main to compensate for temperature or riding conditions.. So you can be sure you have a decent setup every time you ride.

If you know you are going to be riding mainly sandy stuff one weekend, go a little fatter on the main.. If it's wide open hardpack track, you might get away with something a bit more lean.

Have you read the jetting threads?

And when you get it straightened out, get the 3.50 plug that belongs in that bike. The cheap plugs do not like over 10,000 rpm to say the least. How is the pipe and silencer? I would be more inclined to believe your issue is the old crank seals, and you are burning a little tranny oil.

Yeah, not everyone likes the same jetting either. One guy will like the bike to hit harder and another like it smoother. One wants the most top end pull while one wants a longer lasting engine.

Go spend a few bucks on brass and start experimenting.