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Discussion Starter · #1 ·
Hi guys! I think my jetting is close, but I've got a stumble when cracking the throttle in any gear or neutral. It stumbles a bit then goes like a raped ape to redline. Idles great cold and warm. Best idle I've ever had on a recreational machine actually. When riding at WOT, it pulls hard. If I let off for a bend or whatever, and then go WOT again, it takes a second or two, stumbling around, then goes like hell again.

01 660
engine completely stock
Lexx mxe slip on exhaust
K&N filter, no air box mods (everything still there as designed - I like deep water)

Current jetting:
GYTR needles third (middle) clip
25 pilot jets
145/150 mains
2 turns out right carb
3 turns out left carb

Thanks for looking and any help! :D If you need any more info let me know!
 

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I am unique
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Hi guys! I think my jetting is close, but I've got a stumble when cracking the throttle in any gear or neutral. It stumbles a bit then goes like a raped ape to redline. Idles great cold and warm. Best idle I've ever had on a recreational machine actually. When riding at WOT, it pulls hard. If I let off for a bend or whatever, and then go WOT again, it takes a second or two, stumbling around, then goes like hell again.

01 660
engine completely stock
Lexx mxe slip on exhaust
K&N filter, no air box mods (everything still there as designed - I like deep water)

Current jetting:
GYTR needles third (middle) clip
25 pilot jets
145/150 mains
2 turns out right carb
3 turns out left carb

Thanks for looking and any help! :D If you need any more info let me know!
You don't need aftermarket needles if your air is is totally stock as you say.
 

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Discussion Starter · #4 ·
Factory needles back in, just waiting for my K&N filter to dry after a good clean. Will fire it up later this afternoon and let you know!
 

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Alright. Installed the factory needles, everything else is the same as listed above. Still not so good at 25-50% throttle. Still a stumble when cracking the throttle. I made a video that might help!

http://www.youtube.com/watch?v=-5mp7tG0j_Q&feature=youtu.be

If anyone can think of what I should go after please let me know because I have no idea XD
It's sounds like your not enough fuel in that throttle range. Maybe go to a 27 pilot.
 

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Master of the Electron
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No way you need 27 pilots. Raise the needles and/or open fuel screws a skosh. Do one at a time - screws for idle to 1/4 and needles for 1/4 to 3/4 throttle. If it gets worse go the other way.
 

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Discussion Starter · #8 ·
You guys think it's lean? Hehe... this quad is so funny XD... it's rideable but I want to get rid of that hesitation. I'll mess with the needles up and down and see what happens. Runs good otherwise.
 

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I am unique
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Alright. Installed the factory needles, everything else is the same as listed above. Still not so good at 25-50% throttle. Still a stumble when cracking the throttle. I made a video that might help!

http://www.youtube.com/watch?v=-5mp7tG0j_Q&feature=youtu.be

If anyone can think of what I should go after please let me know because I have no idea XD
What size pilots and how many turns out on the fuel screws are you set at............
 

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Im betting you need smaller pilot jets. I would go back to the stock 22.5 if exhaust is your only mod.
 

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Discussion Starter · #11 ·
25 pilots
2 turns right
3 turns left

I do still have the 22.5 pilot jets and yes, all it has is a slip on pipe and K&N air filter. The carbs were cleaned recently when I did the float valves and float bowl gaskets. Float levels set to Yamaha shop manual specifications.

Thanks for all the replies! Got a weekend of camping and riding coming up and I gotta be ready!

Oh, I live in Surrey, BC - and ride anywhere from sea level up to 2000 ft.
 

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Im betting you need smaller pilot jets. I would go back to the stock 22.5 if exhaust is your only mod.
It to Me sounds like a little too Much fuel so even the fuel screws........
 

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I found a screw driver at orielly auto that has a spring so you can bend it up in there. The screw driver bit is in one end of the spring and the handle at the other end. I use a pair of needle nose pliers to hold the end in the bottom of the carb and the spring makes the corner so you can turn it from the side of the bike. I works pretty well.
 

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Discussion Starter · #15 ·
I found a screw driver at orielly auto that has a spring so you can bend it up in there. The screw driver bit is in one end of the spring and the handle at the other end. I use a pair of needle nose pliers to hold the end in the bottom of the carb and the spring makes the corner so you can turn it from the side of the bike. I works pretty well.
I have a springy screwdriver, I'll give it a shot, thx!
 

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Discussion Starter · #16 ·
Okay, I set both carb fuel screws to 2 turns out, and it didn't get any better. Maybe worse, I can't tell really. Seems to run good from idle to 25% throttle, goes to shit between 25% to 75% and is great wide open. Big hesitation when cracking the throttle now.

I'm going to pull the carbs out tomorrow and put the stock 22.5 pilot jets back in. I have a spark arrestor for the pipe that basically makes it the same as stock as far as back pressure goes. Wish me luck! -Tunder
 

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Im running a hmf slip on and k&n filter with no lid and my carbs are setup exactly the same as yours except with stock needles. It runs great. Maybe see what it does if you take off the lid. Or it maybe possiable your carbs need to be cleaned.
 

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Okay, I set both carb fuel screws to 2 turns out, and it didn't get any better. Maybe worse, I can't tell really. Seems to run good from idle to 25% throttle, goes to shit between 25% to 75% and is great wide open. Big hesitation when cracking the throttle now.

I'm going to pull the carbs out tomorrow and put the stock 22.5 pilot jets back in. I have a spark arrestor for the pipe that basically makes it the same as stock as far as back pressure goes. Wish me luck! -Thunder
If it is in that throttle range only, it is the needles, and since you changed to stock needles from aftermarket, and still have the same problem, maybe you need to check if the emulsifier tubes are plugged........
 

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Discussion Starter · #19 ·
If it is in that throttle range only, it is the needles, and since you changed to stock needles from aftermarket, and still have the same problem, maybe you need to check if the emulsifier tubes are plugged........
hehehe... are these tubes next to the flux capacitor?? ;)

now that I've had a night to sleep on it, you guys are probably right. I've been doing some muddy riding and the carbs are probably dirty. when i get home from work tonight, I'm going to check the float levels with a clear tube, and then pull them apart and clean them thoroughly.

thanks for the input so far! i hope this is it!
 

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Master of the Electron
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Inside the carbs the only thing that makes them dirty is evaporating fuel (not riding in mud - it can't get there).

The emulsifier tubes are the small tube that the main jet screws into - the needle fits down inside them - if any of their air holes in this tube get plugged up, the needle section (1/4 to 3/4 throttle) will run like crap.

This happened to me once, and it took forever to figure out it was just mild gunk in the emulsifier tube's holes - of course, it was the last place I looked - I didn't even know it existed. BTW, the factory manual calls it the 'needle jet'.
 
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