Need help FAST!

[clutch22]

ok so here's the deal... KFX 400 .. only run when its choked, at 1/4 throttle it backfires, and wont run when its not choked... is this more of a valve problem, or fuel or what do i need to do.... Really wanna get this fixed, we're leavin tomorrow for the dunes.

[xraven35]

sounds like a fuel problem to me. Have you messed w/ the carb or the jetting lately? Have you taken the airbox lid off?

[clutch22]

Nothing has been changed.... To me, its gotta be the valves... cause for it to backfire they've gotta be floatin or somethin like that.

[xraven35]

yeah, the only working on choke thing is what throws me. check your valve clearances. If one of your intake valves is below spec or negative clearance you have cupped valves, that could affect your compression and cause backfiring if ex and intake valves are open at the same time. I still would clean the carb too.

[Z-Rider86]

What year is the KFX? I have an 03 and the kid who owned it before me said the same thing about my quad when it was his. He took it to the dealer after getting tired of messing with it and they told him that his timing jumped 180 degrees. I'd check your cams just incase something weird happened like it did to mine.

[kfxwizzard400]

check all your vaccum hoses going to the carb this will cause it to not run unless its choked and it will backfire like crazy.. i just went threw this problem and it was a hell of a headache

[CrackerboyLV]

Also check to see if there is an air leak at the carb flange or intake.

[drnez]

Originally posted by Z-Rider86
What year is the KFX? I have an 03 and the kid who owned it before me said the same thing about my quad when it was his. He took it to the dealer after getting tired of messing with it and they told him that his timing jumped 180 degrees. I'd check your cams just incase something weird happened like it did to mine.

Timing doesn't just jump 180 degree's, someone put the cams in incorrectly.

On topic, I would suspect a valve issue, pull you ACCT (auto cam chain tensioner) off and see how many clicks you have left. (remove the center 12mm bolt first, a spring is behind it. Then remove the 2 hex head screws that hold it in, once its off, pull the shaft out and count many times it clicks.)

[Z-Rider86]

Timing doesn't just jump 180 degree's, someone put the cams in incorrectly.

This is true, I was sloppy with my explination. The timing chain was loose allowing the cam to jump 180 degree.