400ex popping carburetor

[crixal]

i have a 2007 400ex. i just put a full ct racing exhaust, k&n air filter, and i run no airbox lid. i went f/ a 148 to 172 main jet. since i've rejetted it has been harder to start and the carburetor pops. if someone knows what the problem is please help me out. thanks.

[gojk]

Originally posted by crixal
i have a 2007 400ex. i just put a full ct racing exhaust, k&n air filter, and i run no airbox lid. i went f/ a 148 to 172 main jet. since i've rejetted it has been harder to start and the carburetor pops. if someone knows what the problem is please help me out. thanks.

Try bumping up the pilot jet to a 40 or 42. Should get rid of it being hard to start.

[RedRider23]

I would think it would be a simple jetting issue, but it could also be a timing issue, I'm having the same problem with my wifes 300ex right now.

cam chain tensioner needs to be replaced.

[BigBore24]

is that what was recommended for the main jet? seems a bit rich to me. i agree with gojk about the pilot. does it pop all the time or just at idle?

[crixal]

yeah, that is what they recommended to me. i think it's jetted for the air box lid on because it doesn't pop when it's on. it pops at about an 1/8 throttle.

[cgndhhh]

pilot jet would only matter for the most part when its just idling, i think between 1/8 and 1/2 throttle it could just be adjusting the carb needle. i agree with bigbore24, im runnning no lid, exhaust, cam, k&N, sparks key, and Je 11:1 416 piston. and im only at a 165 at sea level. altitude might have an effect depending on where ur at as well but 172 seems a lil big.

172 keihin? thats pretty darn big for not having a big bore with a bunch of mods. Try the pilot size up 1 or 2 and try a smaller main

[Pojo450r]

check plug to see if its rich then adj from that also i agree go up on pilot size and check air fuel screw try turning it out 1/4 a turn