CRF's Only Forums

New to the forums and need some help jetting a 2003 CRF450R carb on a kart with a 450R motor on it. Looking for some help or advice. The motor doesn't act like it has any pop when you hit the throttle. To me it acts real lean and hesitates for a second on restarts. Then it takes off and gets above 5k its fine and then we run wide open at 8500-9500.

No airbox just k and n filter.
fmf mega bomb exhaust
stock cam for now.
pro circuit springs and valves.

alt: 800 feet Alabama

Stock pilot
stock needle
main 190


Thanks

With only a K&N and no airbox , i am guessing bottom end lean

Several options:
Go 1 size larger Pilot (#48)
(you did not mention how many turns on Fuel Screw , did you try opening it up *counter clockwise* 1/4 turn ? ,results ?

Try lowering the clip on the needle 1 place (if it was 3 from the top then go to 4 ,etc)

Have you verified that the AP Squirt is just missing the slide and is a strong stream ??

Not having the airbox/filter is going to change how the fuel system is metered and you are going to have to compensate for that