STOP --- PLEASE READ THIS !!!!!!!!!!
This 400EX engine needs your Brains in order to keep me sane. I can't figure out the problem. I just bought a 2000 400EX, at the dealer it ran fine.. Well after about 10 minutes of running, after I got it home, it started to spit and backfire and stalled. Then it wouldn't start again until the next morning. When I finally got it running, it ran fine for a hour or two then died out again. Once again it wouldn't start at all, even after it was warm. It has good gas, just had all the jetting check at a Honda dealer. I mean it's a 2000, like brand new. I know it's not a choking problem or a fouled plug. What else could be the problem here, I needed it fixed like yesterday. If you have any seroius ideas, please let me know. Thank you

 

Could be, contaminated fuel--condensation in carburetor float bowl--trash in carburetor/fuel lines/tank--gummed up/clogged fuel passages/jets in carburetor.

Diogenes

 

Is your battery dead after it stalls?

 

If it were condensation it the carb, how would one remedy that?

Readers don't just answer this question, I'm still looking for ideas. THANX

 

You shouldn't have a condensation problem if you added fresh gas recently. I've been running mine in the snow w/no airbox lid, no problems w/moisture. Do you know anyone else w/a 400 possibly you could switch rev boxes,solenoid,etc.?

 

I just put new gas in the machine.
Keep your brains running for me, would ya. If anyone thinks of anything at all, let me know. I'd really appreciate it. Thanks again

 

Two things come to mind with me.

First, your float bowl on your carburator is incorrectly set too high. Although not likely, because your engine would more than likely start again right away, unless the plug gets temporarily fouled and needs drying time.

Second, it very well might be electrical in nature.

Here's a question and answer quoted from the tech connection on this website.

Question regarding a 1999 Zuzuki Quad Runner LTF 250 2WD:

Problem is that when motor gets hot (driving in National Forest in Texas where there is little, if any, breeze) it shuts down as if it is running out of gas. Fuel supply doesnt seem to be the problem because it will start back up immediately by using the choke but engines runs as if it was a 2 cylinder motor running on one cylinder. It will die right away even if choke is played with. after the motor has cooled down for a few hours, it will start right up as if nothing ever happened.

Answer:

The cause is a heat induced component failure of the ignition system. Any of the following components could be the cause: sparkplug, high tension wire, coil, CD box, ignition pickup, ignition source coil. Test these parts after they get hot and the machine stops. Only then will it become apparent which part is heat sensitive.

Testing all these can be a pain in the butt. Its often suggested that if you have a buddy with a 400ex, then you can swap parts one-by-one to find which component is the culprit.

Hope this helps,
ogre

 

RobRider,
Heres the deal, its new right? It has a warranty still right?
Take it back and demand them to fix it right, you bought a brand new quad and want it to run right, not work on it, if you wanted to work on a quad you would have bought a beater to work on.

I dont know how the Honda warranties go but they should last longer than my Banshee's warranty.

Heres the thing, when I bought my Shee about 3-4 months ago it had a carb problem that I noticed on my first ride with it. I took it back to the dealers and they found out that the left carb was manufactured wrong, to much gas was getting in. Well they ordered me a new one and I was only set back one week without a quad.

If you still have your warranty RobRider, take it back and make them fix it, this isnt normal and shouldnt be a burden on you!

 

Even since its used with no warranty take it back to the dealer and demand satisfaction like repair it or give me my money back they have an obligation that its in good running order even if its used

 

The top choice would be to get that thing back to the dealer with your unsatisfaction..."sqeaky wheel always gets the grease"!

Meanwhile, lets start with the fundementals. It takes fuel, spark, and oxygen to run an engine. We can safely eliminate the air problem since it does run.

The float idea is a good one but it should fire back up...given time to fill. Perhaps the needle seat is jambing up for some reason? Get the problem to occur again and try to start it...assuming that it won't and you'll litteraly flood it! Now, pull the plug and see if it's soaked with fuel...if so, BINGO, no fuel problem.

Spark??? Simply put the plug back onto the ignition wire and groung it to the enginge block while cranking the starter and looking for spark. Cover you and the quad with a tarp to darken it up a bit to "really see".

Spark plugs are funny things, for a few dollars, I'd wack in a new one! Anything else is over my head from here.