Ok hi first i wanted to say this website is great. i stumbled upon this website on accident i am a member of wranglerforum.com and i know how irritating it is to answer questions that if some one looked hard enough for they could find it but i cannot find it. I have a 2001 yamaha warrior. It has a white bros exhaust only performance upgrade. But heres what happend i was at the badlands offroad park and was heading down a hill and go to twist the throttle and it starts backfiring like crazy so after getting pulled to the trailer i started to diagnose heres what i have done. I fully cleaned the carb and the jets, new plug,emptied the tank put new gas in also checked all of the electrical connections .This is what stumps me it idles completely fine but if you give it any throttle it will back fire like crazy and give it to much it will die, and also you put it in choke it will die as well i am stumped. any replies would be greatly appreciated i will be on around 6 pm thanks adam

 

I remeber seeing something about this on another forum something about a broken keyway throwing off the timing maybe this will help.

 

i have a 2005 raptor 350 that did the same thing, i cleaned the carb i dont know how many times, then one day i noticed that there was build up in the inlet of the carb. no gas was going thru the needle to fill the bowl. all i did was take a can of wd-40 with the nozzle and blasted it thru... hopefully this solves ur problem

 

i had the same problem with my warrior. the 97 and up warriors have a switch that goes to the parking brake if the switch is not fully pressed the warrior will not rev above 2500 rpm. if you fix that issue it should work

 

check the voltage coming from your stator. it sounds like the stator might be going bad. this is especially common if you wash the bike with a power washer. while you are in there, you can visually inspect your keyway. if you are getting good voltage from the stator, and the keyway is in good shape, i'd check the coil and the plug wire itself.

if you give it throttle, does it increase in rpm?

i'm leaning towards a voltage issue on this one, but i could be proven wrong and the carb could have a blockage in the air mixture passages causing it to flood under throttle.. out of curiosity, if you leave the fuel on and walk away, is there a puddle under the quad when you return?