Ok....so i went out and bought this 2004 yfz450, brand new. i put bills pipes for the header and silencer, k&n air filter and a gyt-r skid plate since thats all i think a atv needs. i brought it in to get it re-jetted and since i got it back its been riding like crap. around mid throttle it starts cutting in and out of power and the pipe backfires when i deaccelerate. i dont know what to do w/ it. i had the same thing done w/ a banshee and that has had no problems at all. im running the 450 w/ the air lid off and the pipe glows red at night, right were it meets the head. Im thinking the guys that jetted it messed up and so i was thinkin i would just jet it myself since they dont know what theyre doin. any and all help w/ jetting will be greatly appreciated. thnx alot.

 

Whats your elevation and do you have stock needle or NVCQ (YZneedle).

 

What size jets are you running now? The head pipe will glow a little bit at night. usually due to the thinner metal that aftermarket companies use for their headpipes. Where is the fuel screw adjusted too, pilot and main jet size? Also curious do you ride with your lights on?

 

well i dont ride at home very much....so were i do go the elevation is somewere around 1500-2500 feet and i didnt jet it myself. i sent it in to a buddy i know and he did it for me. i ride w/ my lights on only at night. i have no idea what the gas screw is set to or what kind the needle is. all i know is that he used a dyno jet kit ( it also says moose on the box). and that the quad ran better before i got it jetted then it does now. Thank you for your replies.

 

if your pipe is getting red and you are cutting out in the mid to top end range, you are running lean. Is the machine cutting out on top end also, or just on midrange? If just on midrange, then you need to move your needle up to allow more fuel flow at midrange. If it keeps cutting out towards full throttle, you need to change to a larger main jet. You may need to do both...

dave

 

It sounds as if your too lean... A site that offers good jetting info for the YFX is Bluetrax.x..com... So a search.. Eliminate the ".." I posted

Rude Dog

 

Well its only cutting out at mid range. I tried looking for that bluetrax thing but it didnt work. So you think im running too lean and need to move my needle up one? Thank you guys soo much for your help. I'll get the needle moved and mybe change a couple of jets and then i'll tell you guys how its running.
Thanks again.