White plug ,Lean running ?

7 replies to this topic
  • leewr400

Posted November 13, 2001 - 04:00 AM



I posted yesterday about removing the the airbox lid and a slight backfire when shuting off. Last nite I pulled the plug out ant it was very white. The bike idles and starts well and has plenty of top end. Mid range seems ok, but I have nothing to compare it against. If the plug is white, what should be the first mod, raise needle or increase jet size?



  • jamracing

Posted November 13, 2001 - 06:44 AM


If it's white all the way from top to bottom, start by going up one pilot, and check your mixture screw (it should be roughly 1-1/4 and 2 turns out). Next, try going up on the main, and fine tune it with the needle psition. If you go to the jetting topic, you will find more jetting specs then you ever hoped for, but for starters, go bigger on the jets...Good luck

  • yzernie

Posted November 13, 2001 - 06:46 AM



A white plug is ok...sort of!!! I don't jet my bike according to the plug reading. It is an indicator of possibly being lean but there are other factors too. Plug color should not be your primary concern when jetting. Also, if you are running pump gas it will read lighter than if using race gas.

I think you are on the right track by raising the needle one clip position. If the bike is idling ok and runs good on top, raise the needle one position and try it out. I don't remember what your jetting is but in your last post you said it backfired slightly on decel. That indicates a lean pilot.

Sometimes these bikes can be difficult to jet. I have been toying with my jetting for three weeks after doing the BK mod and I think I finally have it right.


  • Chris_Slade

Posted November 13, 2001 - 07:02 AM


My plug was slightly dirty looking when I did my valve adjustment. Remember, this isn't a two stroke, you're not burning oil in the chamber, so it should not be as dark as a 2 stroke. I am satisfied with my plug being as it is, on stock jetting. I doubt the plug should be completely white, as you ARE burning a substance in the chamber, which will absolutely not burn completely. A There should be a small amount of

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  • leewr400

Posted November 17, 2001 - 01:26 AM


Hi Ernie

lowered the clip to #5 position but bike still backfires slightly. It also started to struggle to return to idle, took about 5 seconds. Any suggestions what to try next.

The bike is totally standard.

165 mj
42 pj

screw out 2 turns.




Posted November 17, 2001 - 01:52 PM


Just finished re-jetting my ride with the settings recommended by James Dean. Runs great plug bronze. Lots of power all over. Going to the mountains tomorrow to check it out.

Bonzai :)

  • yzernie

Posted November 17, 2001 - 07:28 PM


Ok, One bigger on the pilot and turn the fuel screw in so it is one turn out. Return the needle to the stock (4th) position. That should solve it. If any problems, get back ahold of me.


  • The_Missile

Posted November 21, 2001 - 02:53 AM


Hanging high on the revs before returning to constant idle is a sign of leanness in the pilot circuit. Try adjusting your fuel screw out by 1/2 turn increments. If you get beyond 2 turns from seated you probably need a bigger Pilot JET.
Fules screw should optimally be between 1 and 2 turns from seated.


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