proper jetting

2 replies to this topic
  • flapwick

Posted September 04, 2009 - 08:37 PM


I have an 02 yz426f.Someone gave me an fmf midpipe and ti4 silencer for it .I would like to know what the most likely jetting combo would be for it.I live on the coast of central california.Twin air filter,and I believe everything else is stock.I asked a similar question about a 1997 kdx220 and had 30 people (with the best of intentions,I'm sure)tell me there was no way of knowing without trying from scratch.Finally,a guy said "go with this size main and this size pilot,and have one larger and one smaller if that doesn't work".His first recommendation was perfect.Anybody out there have a pretty good idea of where to start?Thanks alot,flapwick.By the way.....I have THE coolest looking 426 on the planet!

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  • got5steelman

Posted September 11, 2009 - 05:16 AM


You can do like you did on the kdx, go up one size on the main and pilot, I would install a new spark plug also so after your first ride you can check the new plug for its color, the ceramic should be light brown in color, if white it is lean and if black it is rich. You can also move the clip on the needle, down to richen,up to lean. It all depends on the throttle response of the bike and at what postion the throttle is in what circuit will effect it. 1/4 turn 1/2 turn etc.

  • grayracer513

Posted September 11, 2009 - 06:13 AM





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