Reading Spark Plugs

6 replies to this topic
  • redrider77

Posted October 01, 2004 - 02:21 PM


What do you all make of this plug? Been in for about a month. The bike stutters at 1/3-2/3 steady throttle. The gap was .004 over spec. Also, the air filter was a little over oiled.
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  • RichBaker

Posted October 01, 2004 - 02:51 PM


It's hard to see for sure, but it looks rich to me....

  • Gadsen

Posted October 01, 2004 - 03:47 PM


Easy, running rich, but not abnormal if it was shut down while idling. A good reading will come from going down the road, then shutting it down to read. Also, another tell tale sign is you've been pressure washing it and not clearing out the drain or gettign all the water out. Plug the drain hole in the head before washing it. :cry:

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  • redrider77

Posted October 02, 2004 - 11:37 AM


Just got back from riding. I put in a fresh plug (.024"gap), and a clean filter, and it still stutters from abou 1/3 - 2/3 throttle holding it steady, and started backfiring on decel. (ka-bang, not poppping) Took the air filter lid off and that stopped the backfire, but still stuttered some. Still rich?

  • redrider77

Posted October 02, 2004 - 03:00 PM


UPDATE... It was driving me nuts, so I went out and started fiddling with it some more. I remembered the thread about disconnecting the TPS so I tried that and it seemed to help a lot. Plugged it back in and it went back to stuttering. :cry:

  • wildo

Posted October 02, 2004 - 03:03 PM


sounds like it i would try raising the clip on the neadle a notch or two

  • Dual_Dog

Posted October 03, 2004 - 05:20 PM


I changed the plug in my (used) '02 426 for the first time today. Man, that is a chore. I'm used to easy access with air-cooled motors.

This is what I found. The exterior nut base of the plug was rusty and the electrode area was charcoal grey. I know this bike runs rich. If I ever get motivated to r/r the carb, I'm going to raise the jet needle one position up from where it is now.

The main reason I changed the plug is it took me about an hour to start the frickin' machine when I went riding yesterday. I've never experienced this (maddening) problem before :cry:. I was burned out and I hadn't even ridden 2 feet yet.

Anyway, I changed the plug, gapped it to .032, and the beast fired on the 2nd kick like it supposed to. Runs smoother, too. I'm going to monitor the plug color and if it continues (which it probably will) I'm going to adjust and rejet the carb.


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