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702_smb86

help me with my 03 450

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i just bought an 03 yz450 and the jetting is jacked on it. it runs, and has power, but it pops like no other on decel. it also stumbles on the low end, ive played with the fuel screw, but cant get it to be right, i can get rid of the stumble when idling, but then when i ride it, and pull in the clutch, the rpms like to hang, and take a few blips to die down sometimes. i dont know whats in the carb now, but just give me some baseline settings to start with. im in las vegas, dry, 2200 feet. thank you. sean

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Excessive decel popping is an indication of either a leaky exhaust system, or lean idle circuit jetting. Since you have both decel popping and an off-idle stumble, I'd guess it was lean. Start by making sure that you understand the idle mixture adjustment procedure, and that it is properly set. Then, if there's still a problem, check that the pilot jet is clean, and if it is, go up a step, say from 42 to 45, or 45 to 48.

Something that may help you is the listing of jetting used by different TT members at the top of the index page. Find one that nearly matches your situation and start there.

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I had some low end stumbling on my 03, I put in a JD jet kit and it's a night and day difference, no trial and error with different jets and needles, money well spent, IMHO. Good luck.

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I had some low end stumbling on my 03, I put in a JD jet kit and it's a night and day difference, no trial and error with different jets and needles, money well spent, IMHO. Good luck.

amen..one of the best mods I did on my 03....because it gets rid of the bog and adds better throttle response as well as better pulling power. I also added a quickshot and that adds a little better response

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I agree with Grayracer... it's most likely a lean pilot. I would go up 1 or 2 sizes on the pilot before I messed with the entire jet kit.

Change one thing at a time until you get it right. Then, you can rejet if you feel the need. Besides a pilot jet will cost $5. The JD kit is $69. :thumbsup:

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