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2008 Yamaha YFZ450 jetting?

Dalstdon

By Dalstdon
in Yamaha ATV Forum

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Dalstdon Rookie

Dalstdon

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Hey does anybody know anything bout proper size jetting for a 2008 Yamaha YFZ450? My lil cousin bought it 2 years ago and with the new purchase price has dumped a total of $16000 on this thing! He races it locally so had to remove a bunch of stuff to make it race ready! He didn't do anything to the internal motor to add power, just put on a velocity air filter with no lid on box, scary fast plate for stock carb, and full FMF pipe. All the money invested is in suspension, tires, carbon fiber rims, etc! Somebody messed with his carb and he can't figure it out to get it running again! Our elevation is 550ft up to 1500ft. What pilot jet, main jet, and needle position sounds good to run! Dynojet kit on hand! Thanks guys!

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Ballistik Contributor

Ballistik

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I have an 05 with a full gytr exhaust, stock cleaner and lid on the box. I went from a 158 main,42 pilot and 1 1/2 turns out on the mixture screw to a 168 main, 45 pilot, and 2 turns out on the mixture screw when I put the exhaust on. It runs perfectly . I hope this gives you some sort of a starting point.

the 158, 42 and 1 1/2 turns was the stock setting from yamaha.

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