Lack of power

I'm looking for help with my 02 WR426.My bike has about 450 miles on it. About the last 150 miles or so, I started to notice a crackling exhaust sound (like a small backfire). At the same time I have been loosing power,and throttle response. If I crack the throttle quick at a idle it will usally fall on its face. I live in Michigan, the is about 75 degrees the humidity is about 60-70%. My carb settings are mj 160, I raised the needle clip 1, pilot 42, pilot adj. 1 5/8. My mods are air snorkel removed,FMF Q silencer,and cut the throttle stop. I just did a plug check and it was black with a white tip on the electrode.

Did you make these changes before or after the weather started getting warmer?


First question: you raised the needle or the clip? (Raised needle= richer, Raised clip = leaner)

From what you posted about your jetting, it looks like you could be pretty close to spot on. I noticed that the closer I get to ideal jetting, the more my bike responds to slight changes in conditions. I've had to lean out my jetting a little every few weeks as the weather down here in Florida gets hotter and more humid. If youre plug is black, then it's too rich. Lean it out a little and I'd bet your problems go away. Mine was doing the exact same thing as yours a few weeks ago. I lowered the needle 1 clip and went from a 158 to a 155 MJ. Cleared it right up. It's gotten more humid since then and I'm going to lean it out a little more before the next ride.

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