the wobble most likely is caused by a tire, or tire pressure.
I cut down my seat so it is flat from the tank junction back to about half way, then stepped it back up. it helped ALOT, but is still not 250 mile ready.
tunebike.de can tune these engines to 75hp. he makes a great headder, and offers big bore and porting, and flat slide carb kits. they prep this engine for super mono racing in europe in many different chassis.
shed weight were you can, and that should help also!
I love mine, and would not trade it for almost anything