Im rejetting my 05 honda 400ex that has a 426 big bore kit with a hot cam and a full yoshimura exhaust and I don't know what jet to run or to keep my air box on or what not.

 

If you ever run muddy trails, creek crossings, or dusty areas, keep the air box. As for jettting, once you figure out the airbox ask the manufacturer. They can usually get you close. Sometimes with a high comp big bore you don't really need to go up much if at all because the motor has more suction and can pull more air/fuel mix.

 

When I pulled out the main jet I was running a 160 so I called dyno jet and they said to put a 150 in there since I'm going to keep the air box lid on so I put the 150 in and put the carb back together and first fire up it idled super high at like 3000-4000 rpms do you know what might cause that I've heard the throttle cable?

 

Could be throttle cable is to tight or hung up. It could also run like that from a lean condition. Did you just rebuild this?

 

[QUOTE=Scooter86;3301518]Could be throttle cable is to tight or hung up. It could also run like that from a lean condition. Did you just rebuild this?[/QUOTE



I just put the new a in jet in yes