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chaseboka

jetting, and air/fuel screw

3 posts in this topic

I have a 2005 wr450 and i put a white brothers e2 exhaust pipe on it but i lost the jet that it came with, does anyone have any idea what size it was..... and i was messin with my air/fuel mixture screw because i thought it was the idle screw now it doesn't run the same how do i get it back to where it was..

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The new pipe probably just came with a bigger main jet. Main jet controls 3/4 - full throttle so the rest of the jetting would remain unchanged had you just replaced the jet that it came with. The fuel screw controls idle - about 1/4 throttle along with the pilot jet. Needle taper and clip position control 1/4 - 3/4 throttle. That is the basics of jetting.

Without the bike running turn the fuel screw all the way in and then back it out 1.5 turns, that will be a good starting point. The bike should start with that setting. Warm up the bike and adjust it after that. It should be between 1 - 2 turns out from fully in. If it is more than 2 turns you need a bigger pilot, less than 1 turn you need a smaller pilot. When adjusting it, with the bike running turn it in until it starts to die. Back it out a 1/4 turn or so and see how the throttle response is. Mess around until you get a crisp response just don't go more than 2 turns out or less than 1 in.

Once you have the proper pilot, you should adjust the screw everytime you ride as temps, humidity are always changing and you have to adjust for elevation as well.

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