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High Altitude Jetting

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I have a 2007 KX450. I ride and race between 3000 and 5000 feet above sea level. I am a novice rider. This is my first fourstroke and I am needing some help with my carb. Can anyone tell me what size jets would work the best for my bike at this altitude and what should I change as the weather gets warmer? I have tried to find books covering this subject and have not found anything very helpful. Any advice would be greatly appreciated! Thanks.

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I have the same bike and run around 4300' elevation around here. I've been dialing in my jetting and have it settled into a 172 Main jet, 42 Pilot, 4th Clip down and 1.5 turns on the fuel screw.This is what I had when the temps were in the low 70's last Fall.

You'll have to adjust for the temperature throughout the seasons but that's a good starting point for you. I hope that I can save you a little trial and error since I did it already.

Also, I had a perfect plug on an 85-degree day with a 170 MJ, 40 PJ, 4th clip and 1.5 turns.

Good luck!:)

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