hey there,
I just bought a 03 kfx400 and took it out for my first ride on it today and it seems to have a problem somewhere,the problem is when i go to accelerate from 3/4 to full throttle it dies in power and just bogs down its like its hitting the rev limiter and got no fuel up top.so i got it home put a jet kit through it,im running a dmc slip-on with a k&n filter with a 146main on the 3rd clip with no lid and still seems to be doing it but only on full throttle it just bogs..
would anyone know what can cause this problem...

thanks

 

Im not sure what the stock jet size is, but bogging is from too rich. Id try a couple sizes smaller main jet. Also make sure the diapham at the top of the carb is installed right, and isnt pinched, or torn.

 

If it feels like its hitting the rev limiter and it sputters , then your running to lean. 146 is too small. Shoot for a 150-160 main(mikuni bsr36mm carb). Always better to run rich than lean.

 

I just thought of something. I think your stock carb is smaller than mine. Mine is a 36mm. You might want to try a 160-170 jet.

 

u might need oil because after i replaced my clutch i had a leak in the gasket and i didn't know what it was and every time i would try to accelerate it would start to bog and putting like your saying but seems fine in neutral

 

<div class="FTQUOTE"><begin quote>Originally posted by: K F X STEVE480

u might need oil because after i replaced my clutch i had a leak in the gasket and i didn't know what it was and every time i would try to accelerate it would start to bog and putting like your saying but seems fine in neutral, because if theres low oil there wont be enough and there is a oil sensor that if theres not enough oil it will not run properly or at all

 

When I bought mine the battery was dead. It would jump off and putt around fine but wouldn't run wide open. Check that battery real good because if there's not enough voltage on these 400's it'll bust out just like the rev limiter.