got a 04 p-dub 50. mods-boyesen power reeds,no spark arrestor or silencer,k&n filter. bike revs out good. my son weighs bout 50lbs. from idle to 1/4 throttle it bogs big time. tried diff main jets, just caused it to run rich. play with carb slide and can get some good top end but still no low end. fixed budget. any cheap suggestions?