400ex backfire, missing???? HELP!!

[freestyler04]

I just recently bought a 2001 400ex with very low hours. Upon my first ride the motor would not start. I brought it home and stripped it down then put it all back toghether. It now runs but upon starting and idle it is rough and at low RMP's once every few seconds it will cough exhaust gas out between the motor and carb then die. Once it is warmed up and going it runs ok but backfires a lot and dosent seem to have as much power as it should. Another thing is when I try to go form a bicycle to a wheelie it bogs down and tries to shut off, but this dosent happen when I have all 4 wheels on the grouns. What is happening??? Are my valves not properly adjusted? Do I need to re jet?? I have a pipe, filter, rev box, and no ail lid. Help!!! Already re-jetted to what was recommended. At sea level, mid 70's. please help.:confused:

[1badex]

i would go talk to the person you bought it from.

[freestyler04]

I already did and he claims that he has no idea of any problems.

[ExRacer02]

Take out your spark plug and see how it is burning. This will give you a good idea on where to start on the jetting. I think u are running rich from what you described. Try a 165 main jet and set the clip on the third setting from the bottom. Buy a new spark plug put it in and run the bike for about 5 mins then shut it off. Try not to let it sit and idle. Once it cools pull the new plug out and see how it is burning. I would rather run rich than be running lean.

[freestyler04]

Ok, I changed some things at my local shop. I found an air leak between the carb and motor causing the coughing. The plug had dry fouling going on. I moved the clip to the 4th notch down and the air fuel mixture screw is 2 turns out with a 170 main jet. Runs a lot better now but still bogs when I try to go from a bicycle to a wheelie. Cleaned the float and all but didnt help. Why is it doing this and does it sound like everything is set rite?

[freestyler04]

Ok, I fiddled with my bike a little more. The problem now is at 1/4 throttle and up. Starting at 1/4 throttle the engine stumbles and runs incredibly rough. what is it this time. Help!!

[mustang93]

you are jetted to rich for the summer should be running a 155 keihn main jet

[cals400ex]

clean out the carb. a 155 sounds good. also, the 4th clip position may be a tad rich.

[jt911]

Install an air/fuel ratio meter. No more guesing! Instant feedback.