try doing a search on the site. endless knowledge my man endless. its been done and talked about alot on here. welding a bracket on is probably the hardest part i think although i never done it. good luck.
you can go to your local yamaha dealer and even they can get you slightly bigger pistons (wiesco) at least i was able too get em. they will give you exact numbers there. but that was just to rebuild my engine when the rings went. you cant bore too much on these cylinders otherwise you have to get different ones like cubs or cheetahs. not too familiar with the bigger bores? try a search on here. everything you possibly could want to know has allready been talked about. try it in different ways also.
did you check the simple stuff first like correct gas oil mixture. the plugs good. even if you think there good just try a new set. check for air leaks out of the intake boots(the clamps) hope you find it!!
i remember there was one clown on here that made a sig with (ellisons) pipes in it. he stole his pick of his bike and just focused on the pipes. could that be it???
bent in as if you were looking at it from the front of the bike or bent in like if you were sitting on the bike and the back of the tire is bent in toward the back of the a-arm?? did you hit something?