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Discussion Starter #1
Hey, new to the forum and gotta say up front, I am a pure Honda man, have had 6 and everyone has been amazing...but I do love Yamaha's too. I have been lurking for a hour or two and gotta say that this forum will definitely be very useful to me.

Now that that is over, my friend has a 2001 Yamaha Raptor 660 and he needs me to adjust the valves, new bearings and other things. He said that it ran funny and that it seemed to have a lot more potential. The man that he bought it from said that he re-jetted it. As far as engine mods go, it has an HMF slip-on exhaust, Uni air-filter and airbox cover on. I do not know the jetting in it because I have not taken the carbs off yet. (Dual?? ooohh..nice)

So I took it for a spin and I noticed that it seemed to hit the rev limiter way too early, like a false rev limiter and that it popped pretty bad on decel. So...

What is the stock jetting on this ATV and where should he be around as far as main, pilot, needle and screw?

Thanks, Ian:)
 

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I grew up a Honda guy too, only Honda bikes, trikes and quads for me until 2002. The Raptor 660 was the best choice then and while I keep looking back at Honda I have not yet seen anything from them that makes me want to return.


There's a good sticky on the carbs you can find here:
http://www.raptorforum.com/forums/showthread.php?t=20

Stock jetting is 140L/145R Mikuni mains, Needle in center clip, 22.5 pilots in both carbs.

Here's a sticky listing some jetting specs others have had success with:
http://www.raptorforum.com/forums/showthread.php?t=1461

There are also some stickies here telling you where that early rev limiter might be coming from:
http://www.raptorforum.com/forums/showthread.php?t=60922
http://www.raptorforum.com/forums/showthread.php?t=11734
http://www.raptorforum.com/forums/showthread.php?t=9356

Here's some info on that valve lash check you plan on doing:
http://www.raptorforum.com/forums/showthread.php?t=65410

There's also a procedure for it in the OEM service manual.

Here's the manual:
http://www.raptorforum.com/forums/showthread.php?t=6


And chances are you can find just about anything else you need around these parts. But if you can't feel free to ask and we'll do what we can to steer you in the right direction. Nice of you to help a buddy out and get his running for him, and welcome to the site.
 

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I am unique
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Hey, new to the forum and gotta say up front, I am a pure Honda man, have had 6 and everyone has been amazing...but I do love Yamaha's too. I have been lurking for a hour or two and gotta say that this forum will definitely be very useful to me.

Now that that is over, my friend has a 2001 Yamaha Raptor 660 and he needs me to adjust the valves, new bearings and other things. He said that it ran funny and that it seemed to have a lot more potential. The man that he bought it from said that he re-jetted it. As far as engine mods go, it has an HMF slip-on exhaust, Uni air-filter and airbox cover on. I do not know the jetting in it because I have not taken the carbs off yet. (Dual?? ooohh..nice)

So I took it for a spin and I noticed that it seemed to hit the rev limiter way too early, like a false rev limiter and that it popped pretty bad on decel. So...

What is the stock jetting on this ATV and where should he be around as far as main, pilot, needle and screw?

Thanks, Ian:)
It is possible that the reverse rev limiter is engaging, causing your problem, try grounding the green and white wire from the reverse switch under the drive sprocket and see if this fixes your problem............
 

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Discussion Starter #4 (Edited)
^ Thanks for all of the useful information, it seems like the lid on or off makes a good difference like on the 450r. It kinda sucks because my internet is as slow as dial-up...

Does you have an idea of where he should be as far as jetting if he chooses to keep the lid on and no other additional mods? He probably won't want to take it off because he rides a lot of muddy trails and my 450r is always full of mud!

Should I use Mikuni jets or buy a dynojet kit?
BTW, my elevation is about 1200 feet

Thanks, Ian
 

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Welcome, I am running a factory lid with no snorkle, and K&N filter. I am running #165 and #160 mains with #25 pilot, and the clip one down from center, and I like it.
 

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Discussion Starter #6
Welcome, I am running a factory lid with no snorkle, and K&N filter. I am running #165 and #160 mains with #25 pilot, and the clip one down from center, and I like it.
Thanks, are you using Mikuni or Dynojets? It seems that the numbers do not correspond to the factory Mikuni like on my honda. Sorry for all of the questions, I just don't want him to keep ordering the wrong jets and just want to know what everyone uses.
 

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Thanks, are you using Mikuni or Dynojets? It seems that the numbers do not correspond to the factory Mikuni like on my honda. Sorry for all of the questions, I just don't want him to keep ordering the wrong jets and just want to know what everyone uses.
I used the vito kit, from vito performance.
 

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Welcome to the forum friend!
 

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Master of the Electron
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Welcome to the forum!

With HMF and FULL stock airbox (snorkle completely intact too), try around 145L/150R or 150L/155R mains, 25 pilots (22.5 are stock) and stock needles a notch rich of center.

If you open up the snorkel or the airbox, then start with 160L/165R mains, with 25 pilots and aftermarket needles center.
 

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Discussion Starter #10
Thanks for all of the information, I will have to see whether he wants to keep the lid or not. Looks like I will be buying the Vito's kit, reasonably priced too. Thanks again
 

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I think the vitos kit is a dynojet style numbering (even numbers by 2's up to 150 then by 5's after 150). The Mikuni jets are usually by 5's. For example, Quadmaniac gave you Mikuni jet sizes because the numbers under 150 are by 5's. This was somewhat confusing to me when I first starting jetting too.
 

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The Vito's jet kit uses Mikuni style jets. I just installed mine last month. I believe it came with 165, 160, 155, 150, and 145 mains. Or maybe it went up to 170... there were 5 mains. Also comes with 2 - 25 pilots, aftermarket needles, and finger adjustable fuel screws. Great kit.
 

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Discussion Starter #13
Yeah, I looked on Ebay and the Vito's kit seems the best, plus there fuel screw adjusters will come in handy. The whole dynojet vs, Mikuni/kehin really confused me at first to.

Will try the 150L/155R w/ #25 pilot over my spring break

Funny, i've been looking on clist for a raptor now...
 

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Master of the Electron
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Vitos sells Mikunis jets, not DJ - and it is the most comprehensive kit available.

Equivalent DJ jets would be somewhere around 144L/146R or 146L/148R... but there's not as much info here on the forum for DJ - be aware that the cross references you will find for DJ to Mikuni all over the net are WRONG, unfortunately.
 

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The vittos kit is definately a good kit. The extended fuel screws definately come in handy. You don't have to take the carbs off for minor adjustments anymore!
 
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