I have a built 02 440EX with an FCR41mm carb, full exhaust and a Big Gun CDI. I built it back in 03 and it has been the most reliable machine I have ever owned. Recently it started doing something that it has never done before...........The bike will start up fine, first or second crank like it always has.......then I give it some gas and it feels like it hits the rev limiter at 2000 RPM....missing....popping and just running like garbage. every once in a while it will run perfect for a minute and go right back to how it ran before. I just installed a new CDI, the motor has good compression, valves are adjusted properly and the carb is clean. I put a spark tester to the plug wire and it doesn't seem like it's cutting out........For the first time in the 7 years I have had this quad....I am stumped!

Has anybody else had this problem? I really want to get back on the trail so any help would be greatly appreciated! Call or text me if you want 219-781-0709

 

Could be worn rocker arms. Easy to check anyway.

 

The rocker arms looked fine, nothing out of the ordinary

 

Mine was doing the same exact thing.Took it to the dealer and is was a float or valve thing or something sticking in the carb.They changed it out and ran fine.

 

I guess i would crank up and run it til its starts missing then pinch off fuel line or cut fuel off as the engine starts running out of fuel see if its starts running better before its quits... Alot of times if carb is problem it will run better before dies,Than if no change. Let gets some more history, how long has it been parked before it first started acting up? have you replaced spark plug? have you tried to run without airbox lid on[in case air way has dirtdobber nest inside snorkel?You help us all and we will try our best to help figure out...

 

I'm running an FCR41mm carb and it does start to run better when I turn the fuel off......hmmm.....Maybe I should adjust the float because it's getting too much fuel?

 

Yeah that possible,also an jet could have came loose or fell out...Please get back with us.

 

Did you ever fix this?