00 426 Big Gun exhaust ?'s

4 replies to this topic
  • rmu

Posted July 31, 2004 - 06:45 AM


I got a buddy with a 00426 just like mine, but with Big Gun exhaust on it. We cant seem to get the jetting right on it. It has a serious popping problem when you let off the throttle. Richened up the pilot one step, and the main jet one step off of stock. any recommendations to cure the popping.

  • sirthumpalot

Posted August 01, 2004 - 12:50 AM


Clean the carb before you do anything. You'll never get the jetting right as long as the carb is dirty. The Big Gun exhausts are good, the model for the CRF250 just got a very good review in Dirt Rider this month. Did his problem just start out of the blue?

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  • rmu

Posted August 01, 2004 - 05:33 PM


no, didnt come out of the blue. it's been doing it since he rebuilt the motor at the beginning of last summer. It's been consistently getting worse since then. The carb's been cleaned a few times, and it still does the same thing afterwards. Now, when you say an 01 needle, you mean out of an 01 426, and did you move the clip up 1 from stock position? And, what size did you have your main and pilot jets set to?

  • jespertheil

Posted August 01, 2004 - 09:44 PM


Check that the isn´t getting any false air on both sides of it.. Also check the same on the exhaust.

  • rmu

Posted August 04, 2004 - 03:21 PM


Did a search for the 01 needle, couldnt find anything that explained it. Looked on Motoman's website, but didnt mention anything about it either. Is it as easy as putting a 01 needle into a 00 carb. Also looked at bike, looks like intake boot isnt sealing up totally. hope that helps the popping.

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