Just picked up a 400ex with some problems, need help!

[DVXracer]

Well i just picked up a 99' 400ex, its just been rebuilt (has obvious signs and new gaskets) and the previous owner said it was sleeved to a 440. Other engine mods are pro circuit full exhaust, amr coil, and hot cams stage 2. Main problem is that when you turn the gas on, gas flows out the overflow tube. If i have the gas off it will start right up, but it wont stay running unless i turn the gas on right away, and if i turn the gas on it doesn't want to idle, and if i rev it up, it backfires...

Is the float stuck or just adjusted wrong? Is the float (assuming thats what makes the carb over flow) causing it not to idle and causing the backfiring?

Help would be greatly appreciated. :)

[rubbersdown]

If you have a stock 400ex carb on it the floats are not adjustable but usually dont go bad unless they get a hole in them. Take the bowl off and if your float has gas in it you need to replace it, if it doesnt your probably fine. As far as the overflowing you need to replace your fuel valve and seat and it will stop. This is probably the cause of if running bad too because fuel fills up the bowl to much and the air jets start sucking up fuel.

[AtvKid4Eva]

easier thing is to take the float bowl off and clean everything in there to make sure it isnt sticking open. also check the overflow screw for wear and make sure it is seating when tightened to prevent gas from pouring out, if it is work it willl not seal all the way and cause a leak. hope this helps.

[DVXracer]

Originally posted by rubbersdown
If you have a stock 400ex carb on it the floats are not adjustable but usually dont go bad unless they get a hole in them. Take the bowl off and if your float has gas in it you need to replace it, if it doesnt your probably fine. As far as the overflowing you need to replace your fuel valve and seat and it will stop. This is probably the cause of if running bad too because fuel fills up the bowl to much and the air jets start sucking up fuel.

What do you mean by fuel valve and seal? Are you talking about the petcock on the tank? Or something in the carb?

[rubbersdown]

Originally posted by DVXracer
What do you mean by fuel valve and seal? Are you talking about the petcock on the tank? Or something in the carb?

In the carb. The way it works is the float goes up and pushes a little valve with a rubber tip into a "seal" (brass tube) and that stops the fuel from entering the bowl. If that little valve is warn fuel just keeps pouring into the bowl and starts flowing out of the overflow.

[DVXracer]

Originally posted by rubbersdown
In the carb. The way it works is the float goes up and pushes a little valve with a rubber tip into a "seal" (brass tube) and that stops the fuel from entering the bowl. If that little valve is warn fuel just keeps pouring into the bowl and starts flowing out of the overflow.

Oh, gotcha. Ill check it out today.

[DVXracer]

Alright so i took the fuel valve out (it was kinda stuck, didnt move smoothly) and cleaned it up, now the qyad starts right up and idles... but there are still a couple issues.

No matter where the idle is set, with the choke off, it wont idle higher, it just stays idling low.

With the choke off if i touch the throttle it dies out. Seems like its getting to much gas or not enough...

Sometimes when it dies out it backfires through the carb.

With the choke on, it idles higher, sometimes i can get it to rev up with the choke on, sometimes it dies out if i touch the throttle.

While i had the carb apart i also blew out hte pilot jet. It has a 38 pilot and a 165 main.

I tried getting the spark plug out to see if it was running rich or lean, but cant seem to get it out... i can get my plug socket down there but it wont grab the plug for some reason... whats the secret??

Help is appreciated.

[NMills]

I assume the proper size plug socket is being used? deep enough? I've done it... irritates me...

[sixer3]

I would go up a little bit on the pilot, 40 or 42 wouldnt hurt, when you change it make sure your air/fuel screw is 2.5 turns out from seated, then you should be good to go.

as for the dying on throttle. atleast in my case the bigger pilot helped it

I believe its lean on idle then as you open the slide from giving it throttle you're making the condition even leaner and in your case is causing it to stall

[DVXracer]

Originally posted by NMills
I assume the proper size plug socket is being used? deep enough? I've done it... irritates me...

Yeah, the bigger plug socket wont fit, the smaller one gets down there but wont grab the plug. :mad:


Originally posted by sixer3
I would go up a little bit on the pilot, 40 or 42 wouldnt hurt, when you change it make sure your air/fuel screw is 2.5 turns out from seated, then you should be good to go.

as for the dying on throttle. atleast in my case the bigger pilot helped it

I believe its lean on idle then as you open the slide from giving it throttle you're making the condition even leaner and in your case is causing it to stall

Thanks, ill try and richen it up and see what happens...

[DVXracer]

Well i ran into yet another problem last night when i went out to work on the 400. When i hit the start button, the motor turns over once, then the starter keeps spinning and it sounds like a bad crunching/metal on metal sound... I took the starter off and everything seemed to be in good shape on the inside, and all the gears (that i could see) seemed to be in good shape.

After looking at some break down pictures from bikebandit i suspect the problem to be the starter clutch is worn out?? Anyone else have any ideas? Not sure if i should pull the side cover off the motor and inspect further yet or not...

[sixer3]

honestly sounds like a low batteryt or possibly a sticky solenoid, ry tapping he starter lightly with a small hammer while is clicking see if i engages

[DVXracer]

Originally posted by sixer3
honestly sounds like a low batteryt or possibly a sticky solenoid, ry tapping he starter lightly with a small hammer while is clicking see if i engages

The starter doesn't click and the starter never stops spinning...