needs new plug to start

[Buster]

I have a brand new '04 ex. If I install a new spark plug it will run fine and strong all day long, but if I let it sit overnight it will not start the next day unless I put a new plug in it. The plugs look ok, barely any carbon on them but they won't fire once its sat overnight? Obviously this is not an ideal situation! It doesn't seem like I should have to rejet a stock bike just to keep it running?

[Rico]

It's not the plug but your starting method.

Are you using the choke to start the quad????????????

If you answer YES, then that's your problem.

[Buster]

it won't start without the choke when its cold... not even a sputter

[Buster]

ok, just for fun I went back out to the garage to try starting it without the choke. No luck, at first, I removed the airbox lid and tried it again, fired right up. I resinstalled the lid and it wouldn't start. I think I'm onto something! btw its a CFM airbox. I have some 1" uni vents laying around here somewhere. I'm gonna put those in the lid and see what happens.

[Buster]

messed with it all afternoon.. still no go. I had it started once but it dies if you try to give it any gas at all. After it stalled the 2nd time I haven't been able to get it started again. I get spark but it looks weak.. If I try for several minutes to start it and pull the plug it is wet so I know its getting gas.. but it won't even sputter. Anyone want a 400ex thats still on its first tank of gas?

[6858-400ex]

i have the ehs airbox lid kit works graet:macho :macho

[Buster]

I've got it figured out now. It was the fuel petcock. In the on position it wasn't flowing enough fuel (tank was full). When I put it on reserve and start it up it runs fine until I put it to the ON position.. it will lean out and die.