Reading a Plug

3 replies to this topic
  • tp3dxf

Posted December 12, 2003 - 07:52 PM


Take a look at the attached pictures. Plug Reads

I am trying to get some feedback about the condition of my plug and what it might say about my jetting.

The bike is a 01WR426 it has a complete Big Gun Quiet system. The airbox lid has been removed. I use a No Toil air filter & oil. I also have installed a DSP Power Now. The jetting is bone stock.

The tip if the plug looks ok to me but around the electrode it seems a little black and slightly sooty. I normally ride between 2000'-8000' feet elevation.

The bike runs and starts fine. I was just thinking that maybe I should work on jetting to see if I am getting everything I should be out of the motor.

Any thoughts?

  • Hick

Posted December 12, 2003 - 08:08 PM


I am trying to get some feedback about the condition of my plug and what it might say about my jetting.


Any thoughts?

Those are some good pictures but I'm not sure that I'd want to judge anything based on that.

The accelerator pump in your thumper is a big obstacle to getting reliable information about jetting based on what the plug looks like. This can be a relatively useful tool, I guess, for two strokes, but looking at the plug on a thumper, provided it didn't foul, just seems like a waste of time to me. Just my two cents.

So, how does it run? Based on your mods and elevation (wow) I'd recommend the stock main and pilot, but a stock '01 YZF needle in the stock clip position (4), above 4,000 it will probably run better one leaner (3). Best $14 you can spend on your bike IMO. No kidding.

Hope this helps.

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  • Eddie Sisneros

Posted December 12, 2003 - 08:21 PM


i agree with hick.reading spark plugs just deosnt aply any more.besides the ap,modern fuels have many additves that make plug reading a chasing your tail deal.

the only thing i look for on the plug is signs of detonation.

  • CronicArt

Posted December 12, 2003 - 10:48 PM


I can't see the pic's for some reason. You would read the plugs the same as you would in a car engine. If its black and sooty than its rich. If its white it's lean. If it's oily black you need rings, If its brownish your good. If it's red you have additives in your fuel. The best way to tell is put a new one in, fill your tank and ride it for 1/2 a tank. Take notice to running conditions ie. response, bottom end , mid , and top,. Then go back and pull your plug. Look at the color and consider the perfomance and you can go from there. 2c


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