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400ex carb issues

6068 Views 5 Replies 3 Participants Last post by  shadetree
Hey guys, new member here on the forum but I've been viewing for a little while now. I'm the proud owner of a 2000 400ex that I bought about 3 weeks ago, and so far I have been very impressed and loved every minute of owning this thing! However just recently, It has developed an issue that I need to get figured out.


2000 400 EX
K & N Filter
Wiseco 11:1 Piston
Stage II Hot Cam
White Brothers E-Series Slip on

The story goes: A buddy of mine and I were on a laid back cruise down some gravel roads, mostly just third gear light throttle cruising with the occasional wide open blasts. Quad ran just fine as it has since I bought it. After our ride I loaded it up in my truck and made the 15 minute drive across town. When I got home I took it out of the truck and went to put it in the garage. It started just fine, however whenever I cracked the throttle it would bog out and die. No problem starting back up, but same problem. On half or full choke, it's better but will still bog out and die. I also messed with the idle screw to speed up the idle, and when doing so it will eventually bog the motor out and die also. This leads me to believe that when receiving more air (idle screw/throttle opening) that its starving for fuel and dying.

So, gut instinct tells me that maybe the carb just needs cleaned? Or maybe its something more? If it is the carb, what parts must be removed from the carb for a proper cleaning?

Just curious what your guys' thoughts and opinions are.

Thanks in advance!
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Welcome to the forums... I would start by giving the air filter a good cleaning, especially if you are running an open air box. then I would give the carb a good cleaning also. And dump in a can of seafoam in the tank for added measures.
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