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Discussion Starter · #1 ·
Got an ‘01 raptor 660 that won’t reach the rev limit. It cuts out and pops before it reaches the peak of the power/rpm curve. It pulls strong and revs quick up to 4-5k rpms. It doesn’t stall or fall flat , it just kinda hiccups and keeps going pretty strong but I know there’s a lot of untapped power that should be there. I just can’t reach it.

Mods: HMF slip-on exhaust, k&n air filter w/o box lid.

Not sure about porting or engine work. One of the previous owners was obviously into the motor- there’s blue epoxy where gasket maker was used after taking the head off instead of replacing it with the oem or aftermarket gasket.

when I first got the quad it would barely start , and was backfiring and popping a lot, shooting flames out the exhaust. Yes thre were lots of electrical issues revolving around the rev limiter with the PB and reverse sensor. Someone tried to bypass them and messed up. So I installed a complete wire harness and cdi and new wires To the reverse/neutral sensors. Checked valve clearance- good.Just put on new oem carbs. Old ones were worked on my the same idiot the messed up the wiring probably. That fixed the rev limiter problem but I’m still trying to figure the jetting on this thing and can’t get it dialed in.

stock carbs with stock needles, clip on 4th position. #25 pilots, 160L/165R main jets, fuel screw turns out 2-1/2L 3-1/4R

After I moved the needle clip from 3rd to 4th it seemed to work better, especially the more i turned the fuel screw out on the right carb- I know it’s out a little far as is.

I put the air box lid on and it made things worse. It wouldn’t run at all without full choke .
Took it back off and turned the fuels screws out to 3L/3-1/2R and it revved faster and higher sitting still and ran pretty good, but still cut out at slightly higher rpms than last time.
Should I move the clip again ? Or do I really have to tear the carbs back off and go with bigger jets? 160/165 should’ve been perfect or so I thought. Anything bigger sounds like too much.

please somebody tell me something.

Master of the Electron
15,679 Posts
Welcome to the forum!

You need DJ needles, period. With the open airbox you'll never get smooth transition from 1/4 to 3/4 throttle without the aftermarket needle's more aggressive taper.

Your last paragraph makes NO sense. Lid on IS richer - requiring choke is exact opposite of what should happen.
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