Hi everyone. I honestly can't go through those 2600 pages or so of past posts to find a similar issue with my 03 yamaha raptor 660. It has a k&n DG exhaust ...carb has 25 and 140/145 and needles at 2nd clip from the bottom (towards the point) it runs fine till about 3/4 throttle then starts to struggle almost dies then back fires then it goes good for 3 seconds then starts over. Carb has been cleaned very well and has new o rings and gasket..both springs are matched to spec kinda lost..do I need a 150/155? And needle set at the middle?

 

take carburetor off and let it fill up with gas remove the bowl and make sure you are getting enough gas sounds like you are running out of fuel in higher rpm if so adjust float to allow more fuel..

 

I did that today actually with bigger jets and runs alot better now...get the odd snappy back fire once and a while but still can't hard hot the gas from idle...u can see alot of fuel pour in so adjusted the needles and removed the washer inside...I went to a 160 165 too much money to get some in betweens.

 

okay now you need to back your fuel mixture screw out a 1/4 turn to allow more air maybe even a 1/2 turn

 

Are you running with after market exhaust and air filter they are required for jetting to stage 2 and larger

 

Okay seen you have kn filter and dg exhaust if problem still occurs after adjusting mixture screw move clip up one notch on needle. Hope this helps you

 

I thought the air mixture screw was only an idle thing? I don't really want to remove the whole intake assembly again.....did it about 17x yesterday lol but has to be check fully assembled to get accurate readings. Both screws are at 2 1/2 out and no hesitation on idle or above 1/4 I decided to modify my own jets going to the local dealer was over 100 bucks and that's getting a little much. I did adjust the needle to the lowest point and runs pretty good just like I said has that sputter once in a while