Lean or Rich?

2 replies to this topic
  • slowjohn

Posted March 08, 2006 - 01:26 PM


Hey folks,

Just bought me a new 04 WR450f a few months agonn. So far I think it's the best purchase I've ever made (other than my son's pw50). I'm pretty new to the dirtbike world and after reading many many posts on here I'm wondering...how can you tell if your bike is running rich or lean?

Thanks in advance,

John :thumbsup:

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  • dbailey223

Posted March 08, 2006 - 01:35 PM


I believe that the best way is to the ole spark plug test. I've never done this whole approach, but this is what I have read here, if I summarize it right. RUn the bike at a good rpm on a fairly level and straight stretch for a considerable period of time. Pull in the clutch and hold it, then kill the engine with the clutch engaged. Then, take out the plug and see if is white (lean), black (rich), greyish tan (right on).

Short of that, if the bike bogs, it is ?????, and if it sputters, it is ???. Someone who knows will have to fill in the ???

  • Indy_WR450

Posted March 08, 2006 - 03:50 PM


Forget the stock jetting! You are lean! No need for a plug chop. Look at our forums pinned jetting post at the top of the first page and you will find this as a good base jetting:

168 main stock needle in clip #4, get a 48 pilot, zip-ty adjustable fuel screw and a 72 starter jet. replace the stock cork with an aftermarket insert like PMB or GYT-R remove the snorkel from the air box and you should be good with this jetting most of the time in Kentucky. Drop the main in the summer to a 160 if you get a lot of cutting out at open throttle. :thumbsup:


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