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450 EXC Jetting/05

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James, I still need help!

Okay, brand new bike, 3 hours on it. Installed right from the get go a 42 pilot, 172 Main and the Blue needle, 3rd from the top. Fuel screw 1.5 & 1.25 turns from full lean/turned in. Altitude was 4000-6500, with a temp. of 57. Head pipe only turned yellowish. On start up when cold, back-fire through carburetor. Little smoke from what appeared and smelled like unburned fuel. When warmed up, no smoke, but ran poor. Under load, seemed to run fine. When I chopped the throttle, no back-fires or popping. But, when the throttle was at a position of no-load/load position, “just at that fine point” it would cough write at the deceleration? Now what?

For a little more information, my head-pipe was not at all blue like my buddies who ran stock needle, 42 main and a 165 main, clip in the third. His bike ran spot on. “stock needle/jet. However, from the appearance of the head-pipe, looked a little lean?

Look forward to your help.

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I know I'm not James, but have you tried the red needle? I would give that a try, but in the 4th or 5th clip postiion.

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The red marked needle in the 5th from top clip position is a good alternative in this case. The bike will run cleaner at low throttle positions and idle.

At 4000-6500ft elevation, a #170 main jet is usually recommended.

Thanks,

James

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