I have a 2001 Raptor 660. I just put a White Brothers E series full exhaust system, K&N jet kit, K&N filter with the billet mount, a aftermarket CDI and rectifier, then drilled two 2" holes in the air box. I ride in the mountains a lot so I jetted it for 6000 and above but I test rode it at about 3500 feet. At full throttle it sputtered like it was starving for more gas. At less than full throttle it seamed to run just fine. Could anyone suggest a fix for this problem?

 

when you are sitting at idle and give it full throttle and let go fast does it backfire on the way back down?

 

Nope. It didn't backfire at all. Jetting?

 

Sounds like the main jet.....when I put my exhaust and jets and everything in my scrammy...It would run fine all the way up to about 75 percent throttle..then when I gave it full gas it just wouldn't go...it would sputter also...it wan't to go but it seemed like it was deprived of something....well to get to the point your main jet is for full throttle...75%-100% so if your main jet isn't allowing enough gas to through through it then your going to sputter since its deprized...I would say I'm about 90% sure its your main jet.

 

THere is your problem right there.....jet your quad for the lowest altitude you ride at so you do not lean your engine out.
Gary

 

try two sizes bigger on the main

 

Try putting some tape over those holes you drilled. If it runs fine it was lean.

 

was the choke on?

 

Thanx, I'll be working on the problem in a couple weeks, honey-do-list has been stapled to my head, can't dodge the "priorities" any longer. Guess I should be happy I got to sink $1000 into the quad. I'm sure it's the jetting but I will post my results as soon as it kicks the DS 650s butt all over Utah.

 

Ya, post your fix once you get her running good!