[Rb30man]

New to this forum, kinda confusing

So i have a 06 crf450x which i just rebuilt with a 13.5:1 piston and have add a 08 crf450r head and cam, was wondering what size main jet i should use, the jet in there at the moment is 165?

Any help is appreciated, cheers.

[JimDirt]

Jetting is based off a few things , from elevation , to air temp , etc , this chart was made by the resident carb guru here , go by it and you should be good

Jetting Guide for Main Jet:(pilot 45) CRF450R/X

Sea level....165
2000 ft.......162
4000 ft.......160
6000 ft.......158
8000 ft.......155


Temperature/Elevation:
One main jet size (up/down) for every 2,000 feet or 25 degrees in temp.