400ex Troubles

[400EXSTUDMUFFIN]

I have bought an 01 400ex and the day I bought it the bike was running great!!! I rode it at the guys house I bought it at and after my 5 hour drive home I rode it again IT RAN GREAT.

It's an 01 400ex with a K&N and a full R4 Exhaust he did not jet the carb cause WB told him it would be fine

He also told me the bike fauls plugs evey so often I thought nothing of it till today when I tried to crank my bike and it sjipped abd backed fired ans would not run. I changed the plug and it started right up I took it for a little spin to see if evey thing was ok and it ran great up itill you give it over half thottle??????

So the bike cranks and runs fine as long as it's not above half throttle

If above half throttle then I just bogs and thats it

What could my problem be??????

Any help please

[K_Fulk]

Try bumping the main jet up a size or 2. It sounds like it may not have enough fuel on the top end. Even if it doesn't fix it you will only be out 10 dollars or so. But it sounds like its lean with the k&n.

[ewalker302]

You def need to jet a stock bike with a full WB-R4 & K&N.

You will need to go up 1 maybe 2 sizes on the main jet & raise the needle valve 1 spot (lower the clip 1 position).

You can also go out to 3 1/2 - 4 turns out on the air/fuel screw to richen the mix some.

:bandit:

[cals400ex]

yep, try rejetting. i would probally just get a 40 or 42 pilot jet instead of going out too far on the fuel skrew. i think you are suppose to get a larger one when you are at 3 turns out.

[400EXSTUDMUFFIN]

Thanks a ton guys I am sure this will help

Also I live in jacksonville fl do you think the choke mod will work for me it does not get to cold here!

I want to try it but I also want my bike so start with ease

[cals400ex]

i did the choke mod and thought it was a waste. i put the choke back in. i put a larger pilot jet in and it still wouldn't start without the choke. i have no clue what the problem with my bike is. i can always get it started with the choke though, even in zero degree weather. most bikes will fire right up without the choke and a larger pilot.