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TTR250 running on... after full throttle

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Does anyone have an idea what the problem may be with TTR250 that seems to want to run on after full throttle. When I back off on the throttle it seems to give an extra spurt of power before it backs off, bit annoying when you come flying into a corner and the bike wants to carry on going. My bike is a 2006 model, not sure what jets are in the bike as the local Yamaha dealer has tried to sort it out. They also removed the snorkel, drilled holes in the airbox after I fitted a DRD pipe on the bike (a YZ450F pipe that has been modified to fit).

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Full throttle is the main-jet, which if you've got a less restrictive pipe and opened up airbox should be a 140 small round main jet (Mikuni N102/221). The pilot jet should be a 52.5 or 55. Also, the needle should be raised up a notch or two and your fuel-air mixture screw brought out to smooth idle on a warm engine. The airbox should be opened up to be about 2.75" square inches, no more, no less.

None of these things are hard, AT ALL, and if you can turn a screwdriver and read you can check these and make the bike right.....chances your dealer is haplessly trying shit hoping it works....and without knowing what's going on inside the carb or on the bike you're going to keep guessing. I'm a mechanical doofus, and if I can do that stuff you can too....don't fear tearing into it. I'm sure there are people local to you who are willing to help you out if we here can't give you some assistance.

Read this thread, has all the info you need:

http://www.thumpertalk.com/forum/showthread.php?t=339411

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Full throttle is the main-jet, which if you've got a less restrictive pipe and opened up airbox should be a 140 small round main jet (Mikuni N102/221). The pilot jet should be a 52.5 or 55. Also, the needle should be raised up a notch or two and your fuel-air mixture screw brought out to smooth idle on a warm engine. The airbox should be opened up to be about 2.75" square inches, no more, no less.

None of these things are hard, AT ALL, and if you can turn a screwdriver and read you can check these and make the bike right.....chances your dealer is haplessly trying shit hoping it works....and without knowing what's going on inside the carb or on the bike you're going to keep guessing. I'm a mechanical doofus, and if I can do that stuff you can too....don't fear tearing into it. I'm sure there are people local to you who are willing to help you out if we here can't give you some assistance.

Read this thread, has all the info you need:

http://www.thumpertalk.com/forum/showthread.php?t=339411

Thanks for the feedback, must open up my carb and have a look what jets are in place, by the way I forgot to mention that I ride the bike at an altitude of around 5 500 feet above sea level, will this effect your suggestions?

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Thanks for the feedback, must open up my carb and have a look what jets are in place, by the way I forgot to mention that I ride the bike at an altitude of around 5 500 feet above sea level, will this effect your suggestions?

You're probably still pretty good on the jetting I listed. I've seen guys running that same jetting up into the 6k-8k range and reporting a good mix. If it's not right, it's pretty damn easy & cheap to unscrew a jet and put another in...you're talking less than $15 for both jets and less than 1/2 hour of your time.

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