ok so i just bought a 97 warrior that has been recently rebuilt (motor) and they put a big bore and stroker kit in it and a mild billet cam, ported and polished and well it still has stock jet. and well it does not like low end rpms not getting enough fuel. so i am wondering what size jet to install. any help?

 

What exactly is it doing? Is it backfiring alot or loading up and dieing?

I just did a similar build on another bike and was suprised that the jetting didn't change much (pilot went up 1 size while main stayed the same). Unless you added a pipe and air filter to allow more air in/out there won't be too much difference in the jetting.

If used high comp piston or longer duration cam then jetting may actually need reduced.

 

its got a pipe and and not a high lift cam. its just very sluggish at low rpms and if you come down from high rpms it boggs down.

 

The bogging could be primary jet too big or even air/fuel screw not adjusted correctly. Sounds like it's rich. Put in a new plug and let it idle for 20 mins. Pull the plug and check the color. Black is rich, white is lean.

How does it run at half throttle and up?

 

I always left the pilot jet stock and just went up on the main jet on my built Warriors and they usually ran great. I forgot what size jet I ran, it seems like a 147 - 150 main might be close for an aftermarket filter and airbox lid with holes in it. That jet worked good for anything from just a filter/modded airlid and slip-on to a full blown 446 stroker that was running with stock YFZ 450's. But you have to remember, a stroker engine will run richer with the same setup as a stock crank, because the downward stroke is longer and has more time to suck in more air/fuel, causing it to run rich. What really determines your jet size is how much air you're moving, that means what filter/filterbox/lid setup do you have and what kind of pipe/silencer you're running.