The whole x15 engine has gonernors...they have to be systematically upgraded and modded to perform as they should.........
Theres the crappy plastic CDI that loses its potency as it heats up.....
The fuellines are restrictors,,you need to upgrade to 1/4"
Theres the float restrictor tab in the floatbowl
Theres a sloppy weld in the headpipe that needs to be opened up with a grinding stone
The stock snorklebox has a restrictor disc inside it,,,plus the snorkle box is crap
The amount of excessive crankcase pressure and heat build-up at the valves causes poor performance...a headbreather kit works the best at removing heat from around the valves/valvesprings...It also helps powersuck the crankcase presure out aswell to enhance revs
The rest are internal..The valvesprings need to be changed with quality honda springs to control valvefloat,,the transmission gears need to be radiused and polished,,the shift drum grids need to be smoothed and the shift forks need to be polished,,,the clutchpack needs to be blueprinted,,flywheel needs lightening aswell as balancing,,oil passage needs to be enlarged to 2mm's
When youre done you basically could have bought a bike with a Japan built engine to save all the headaches.......