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View Full Version : 400ex backfiring and stalling


Stigsxr
10-20-2006, 06:38 PM
My 400ex is backfiring while riding and when you left of the throttle and let it idle it will stall immediately? Any help would be appreciated.
John Pennella
10-20-2006, 06:49 PM
Is the motor stock or was there things like carb work done?
Warrior-mx
10-20-2006, 11:06 PM
Richen up ur low end (pilot jet) that should stop ur stalling prob and check ur plug if the electrode is white take the main jet up untill it stops. An i deal color is a brown-tan color. And if the plug is black take the main jet size down. ANd check 4 exhaust leaks or intake leaks because these to lead to back fire.
Stigsxr
10-21-2006, 08:10 AM
Originally posted by John Pennella
Is the motor stock or was there things like carb work done?

Yes the motor and carb are stock.
Stigsxr
10-21-2006, 08:36 AM
What should the air/fuel mixture screw be set at with a stock 400ex?
Warrior-mx
10-21-2006, 08:42 AM
2 1/2 turns out
Aceman
10-21-2006, 03:21 PM
If you haven't changed anything on your quad and it just started doing this it's most likely a fuel problem. Clean your carb out and blow through all the holes with compressed air and carb/brake cleaner. When you pull the fuel hose off the carb, turn the gas on and make sure you're getting full fuel flow out of the tank. If you're not there is a screen in there that is plugged with junk or your vented gas cap isn't letting air pass through it.
Stigsxr
10-22-2006, 09:42 AM
Originally posted by Aceman
If you haven't changed anything on your quad and it just started doing this it's most likely a fuel problem. Clean your carb out and blow through all the holes with compressed air and carb/brake cleaner. When you pull the fuel hose off the carb, turn the gas on and make sure you're getting full fuel flow out of the tank. If you're not there is a screen in there that is plugged with junk or your vented gas cap isn't letting air pass through it.

I cleaned the carb yesterday and it was stilling popping and stalling. Then I rode it around for alittle and it stopped and idle perfectly. I started it back up today and it starting popping again. I didnt warm it up yet, so ill see if its only popping cause its cold.