rough starting

[hondaripper]

i recently bought a 2002 400ex with a 426 big bore kit, full big gun exhaust, ported and polished head and it was jetted for the exhaust. my problem is that the thing is a pain in the a** to get started it will start then instantly stall a few times then will start and run a little longer and backfire and then once it starts to warm up it will stay running but wont iddle intill its fully warmed up, then once it warmed up it will run fine no backfireing and it will iddel fine, and i can shut it off and it will start no problem as long as it hasent cooled down. i was wondering if maybe the jetting makes it suck to start in the cold, because when i bought it the guy had it in a heated garage and it fired up no problem. any help would be great it sucks to watch my friends riding when im still tryn to get my quad to start.

[JOEX]

Bigger pilot jet will probably be the fix.

[Aceman]

Like Joe said, if it's backfiring on startup, I'd start by going 2 sizes up on the pilot.

[nick249420]

mine does the same thing but its stock

[JOEX]

Originally posted by nick249420
mine does the same thing but its stock
The cold weather may require a jetting adjustment...

[nick249420]

eh ..
mine does it cold or warm weather
once the bike has warmed up its fine start with ease

[hondaripper]

well it worth it to try a different jet size only i dont know what size is in there now anyone know how to measure it

[Aceman]

When you take the pilot out, the number is stamped on the side. Same with the main jet.

[hondaripper]

thanx

[honda300EXtreme]

odds are its jetting,, but its also possible that the valves are too tight,,

usually when the intake valves are tight the quad will not idle untill warm..

if jetting does not fix it,, i would check/adjust the valves

[hondaripper]

i ahvent gotten around to trying to change the jets yet "been busy" but today i went to fire it up to take it for a quick ride and it would fire up and run with the choke on but as soon as i took the choke off it would pop and stall out and then not wanna start back up. i thought it might be flooded so i held the throttle all the way open and held the start button to clear it out and then it fired up againe but it would do the same thing now i know running it witch the choke on could possibly flood it because your running it with more fuel but when i would take the choke of it just seemed to flood so i dunno wtf is goin on

[250exkid]

i heard go up to a 42 pilot jet

[JOEX]

Check for air leaks around the carb boots, make sure the carb and air filter are mounted correctly.

[Aceman]

Come on man, I've posted this once already. YOU ARE LEAN! Go up on the pilot! Partially closing the choke restricts the air flow, which richens the air/fuel mix. The engine is telling you it needs more fuel to match the air flow through the carb. I can't put it in simpler terms than that........