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Still can't figure out my 2005 Yamaha Raptor 660!?!?

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I posted a question last fall to try a figure out why my '05 raptor 660 runs so poorly after a local shop worked on it. They insalled the jet kit and cdi. It starts cutting out past about 3000 rpm. It feels like it is starving for fuel. Does not cut out at exactly the same rpm but close. If you play with the throttle (ease into it back and forth a little) it will eventually rev up but still cuts out when you hammer it!! This only happens when riding it... in neutral it revs straight to govener with no hesitation.


gytr jet kit

k&n filter

D&G exhaust(slip on)

CDI box (Ricks motorsports hot shot)


replace cdi box

new jets- stock runs 140 & 145, shop installed 145 & 150, I installed 150 & 155 (dual carbs)

Adjusted air fuel mix a thousand times!!!

removed parking brake saftey switch

tested coil


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I agree, that definately sounds like a jetting issue. Why are the carbs jetted differently? Have you tried different pilot jets or needle adjusments? Make sure the float bowl vents are clear and that you have no intake air leaks. Also make sure the choke mechanism is workin properly.

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I changed the mains twice, adjusted the needle, inspected the choke, and checked for leaks. I did not change the pilot yet because the only way i can get it to climb in rpm is with a small amount of throttle but will try anything at this point!! For some reason the carbs are supposed to be jetted that way ( can't remember why). I am not familiar with float bowl vents but again will try! oh and the things i did try have not changed it at all

Thanks for your suggestions my fiance really wants to ride. We both appreciate any thoughts!!!!!

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The thing that makes me think your pilot may need to be changed is that you can't get past the lower end of the throttle range whithout babying it. That is the part that the pilot affects, the lower throttle range. Is your air box lid modified or removed? Are the carbs sync'd properly?

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The air box lid is not modified and it is on and they are sync'd. The way I understood it is that pilot would only help in the idle to 1/4 throttle range. It stumbles the worst at about 3/4 to full. Stumbles a little less but sill bad at about 1/2 to 3/4. And it runs great before i hit about 3000 rmp +/- at any throttle position. But I would try it if you still think that might be the issue. It is hard to explain exactly what is going on so i am trying to be clear. I thank you guys again for you thoughts and am going to pull the carbs back off and check in regularly to see what you think.

I forgot to ask which way with the pilot.

Edited by mwilliamson

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I misunderstood where you were having the problem, it does sound like the pilot is ok. Do your carbs have adjustable needles? You may try adjusting the clip 1 spot in either direction and see if either helps if they are. If not, try dropping one size on your main jets at a time until it starts to clear up. It sounds like it may be running rich, to me. Did it run better or worse when you changed to bigger jets than what the dealer put in? If it ran worse after you re jetted again, then I would go leaner, I would try 142 and 148. If it ran a bit better, when you re jetted then try 152 and 158, if that makes things worse, then maybe you just went a bit to far with the 150 and 155, so then try 148 and 152.

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Thanks for the idea. I just got married and went on a honeymoon so havent had much free time to check this out. Back to the real world now lol.

Changing the jets or needles have not helped or hurt the problem one little bit. did not change it one little bit. i have switched back and forth a million times and have a hadful of jets. Heard a idea from a mech i know, how about the stator? i heard a rumor that they are hard to test accuratly but did test it and showed resistance at .8 book says .45 to .65 is good.

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First off, congratulations on the marriage, I hope you have a long and happy one.

I added some info to your thread title and moved it into the Yamaha section.

Well, it is certainly a possibility, a weak stator can make the machine run badly in alot of different ways. I can't believe that didn't occur to Stoopidbot or I. Since jetting has obviously not changed anything, I would agree that looking into the ignition system is the next logical step. Before buying a new stator, I would try to test any other ignition component that there is a test for, like the coil, a new coil is alot cheaper than a new stator. Another thing I would check is the connection between the plug boot and the coil wire. The boot should just screw right off of the coil wire, make sure there is fresh undamaged wire at the very end for the boot to screw into. If not, just trim the coil wire back in small increments until you find good wire at the end. If it does turn out to be the stator, which I think is most likely after reading about your problem again, an aftermarket stator may be a good idea, Ricky Stator has been making quality ATV parts for as long as I can remember, and their stator is half the price of an OEM stator. Here is a link, check it out.

Ricky Stator

Edited by DirtDemon

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Thanks. Good deal on the stator!! I appreciate the heads up on that. Will check it all out. Good idea about the wire. i had the shop check the coil. said it was good.

Thank you for the ideas everybody!!

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We forgot one important thing: he's from COLORADO- ALTITUDE!!!!!

what's your altitude? if it's over 4000 feet then installing bigger jets will make it worse not better. You have thinner air there just like here where we ride 4k to 7k feet.. We cut a hole in the airbox lid and run stock jets and they run just fine. You have less air because there IS less air, so you need less fuel, not more.. Buy a new plug and do a plug chop test- that will tell you if you are rich or lean. let us know!

Yes 660s have 2 diff jet sizes in carbs sitting side by side. One has the choke in it and the other does not. It has something to do with the three intake valves.

Josh you had the right idea.

Edited by Raptor8

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I didn't figure the elevation would be an issue since it ran fine there before he had the work done, but I can see how his problem could be a lack of airflow to go along with the modifications that were made. So it makes sense to jet a bit richer for the mods, but maybe he also needed more air than he could get throught the stock lid, even with the aftermarket intake. Been almost 2 months since the last post, I wonder if he has fixed it yet? Maybe a an open airbox is just what he needs.

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heard it before, "It worked fine until I fixed it." LOL:laugh:

What we do here for those who go to the coast is cut a hole in the airbox slightly smaller than a piec of ductape. Open when here at altitude, tape over it when ya get to the coast. They are all factory set for sea level.

I run FMF pipe, cam, and a few other yamaha parts and it has run fine for 10 years now.

Did I explain it so you could understand it? higher alt = less air= less fuel needed. if you jet bigger you are going rich= not needed.

hope this helps! I forgot all about lookin at the date! :mad:

Remember #1 technicians rule: If it works, don't fix it.

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I know exacly what you mean by the elevation thing, there is less dissolved oxygen in the air at higher altitudes, just like there is less dissolved oxygen in warmer air. Less air needs less fuel, but more fuel needs more air, so as you pointed out, a hole in the air box may be just what he needs. However, I also wouldn't rule out his suspicion that his stator is bad. He did say that changing the jets, leaner or richer seemed to make no difference, and his stator did not present proper readings when he performed a direct resistance test.

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that's wild. I guess it's possible, but I have never changed a stator on a 660. never.

who knows- that could be it.

This is like doing surgery over the phone- it's almost impossible to diagnose/repair a patient when it is 2,000 miles away. All we can do is give people tips and try and lead them down a diagnostic path....


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Agreed, all you can do is shoot out ideas from here. It is so much easier to fix things you can put your hands on. I guess if he ever comes back we may just figure out what the problem was.

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I'm what most would call a workoholic. work more in two weeks than most do in three or four. I have not even had a min to look at it. I do appreciate all the input and am not looking for someone to fix it but when i look at this and have people throwing out ideas it sure helps. 3,4,5 brains can be much better than one. thanx everybody!!!!

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