400EX Will Not Stay Running

[bsummers12]

Recently I rebuilt my Daughters Boy friends 400EX. New piston, rings, valve guides and had the valves lapped. After putting it all back together I tried to start it. It would only run for a brief time, approximately 30-40 seconds. So I thought, okay maybe the carb is gummed up and the needle valve is sticking. I tore the carb apart and cleaned throughly. Re-installed it and had the same thing happen. So then with the advice if a friend I re-adjusted the valves again. Started it up and it ran for approximately 3-4 minutes and idle and high RPM and when I went to adjust the choke it died and I wasn't able to start it again.

Am I having a lack of fuel problem llike the bowl is running dry or am I getting to much air and not enough fuel? I tweaked around on the pilot valve some according to the manual lightly seat and back off 2 1/4 turns.

This bike is starting to frustrate me and I could use some additional guidance.

Thanks,

Brian

[sprayedgt]

Sounds like the bowl is running dry. Make sure the float works properly.

[bsummers12]

So in other words drop the bowl and fill with fuel to see if the float raises?

[sprayedgt]

You wouldn't be able to see it since the bowl covers it up. Take the carb off and make sure the float moves freely. Sometimes dirt can get in there and keep it from moving properly.

[79400ex]

also, make sure the tank is vented.

[midwest honda]

Did idle seem to hunt up and down?

If so you have a lean condition. Although i dont understand why unless you had it apart for a long time. Check you fuel tank for vent like 79400ex said and make sure your carb isnt slowly loosing fuel somehow.