I have a 2001 Raptor 660 with some add ons. I got a White Bros E full exhaust syst, K&N Pro design w/outerwears, Dynojet stage two, after market CDI, two 3 inch holes drilled in the box. I had the mains set to the 3000-6000 setting (144L 146R) and it ran terribly at above 6000 ft, now I have the carbs set to Dynojet specs above 6000ft (142L 144R, needle set to the 4th groove from top). I ride mostly above 6000 feet in the dry climate of Utah. Even after the jetting change it still runs the same (same elevation) crapping out at mid throttle while trying to power up a steep incline. After I stop and try to start it back up it blubbers really bad until it eventually revs up and seams to clear out. While on relatively flat trails it seams to run better. It never backfires and revs up to full throttle without sputtering, it's that mid range throttle position under power where it craps out especially when I let off just the littles bit it dumps all power. I hate re-jetting this thing as you know the work it take to just get to the carbs main jets!

The easiest fix is to just get a 06 700R YFI huh?
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First off, I would try taking the air box lid off and see if this helps or hurts the situation.

 

Yeah, I tried that in the middle of the ride. It didn't help or hurt the situation.

 

If it is in the mid range, you need to move the clip up 1 position on the needle jet, and ride it. If it stil craps out you need to move it up again. also if you use the dyno jet mains, you must use their needle.

 

I have been reading up on jetting and it seams as if it (needle) does need to be moved up one position according to my situation. I was thinking of trying this next. Tell me something, If the mains were not jetted correctly (they should be according to the Dynojet instructions)what would be the symptoms then? I mean, after the episode of power loss I rev the hell out of it and it revs to full throttle fine, of course this is in neutral and not under power.

 

Well you know what it feels like now {bogging at mid range}, It would feel the same only at wide open.

 

I am also having this same damn problem. I bought a 2001 raptor used 2 weeks ago and the dealer can't figure it out either. Basically he's telling me the bike is fine and I'm just nuts. But of course they put it on a dyno for a half hour and it ran fine, I go back and take it for a ride and you know it, same problem. So if you hear anything help me out and I'll do the same because my mind is ready 2 explode.