Sooty spark plug

4 replies to this topic
  • johnhab

Posted January 03, 2002 - 03:59 PM


Maybe someone can give me advice about my 2001 YZ426. I had it start missing and popping this summer after riding it for four months. It always starts and idles fine and will run fine for a couple of weeks before the plug goes bad and needs to be changed. It doesn't seam to be a jetting problem because it runs to well, and I follow the YZF rules of not turning the throttle when starting and letting the air filter sit for a couple of days after oiling before riding. I went to a CR7E and this helped but it still doesn't last long enough. I sometime take off to quick after starting and I think this is part of my problem maybe the bike is to cold to burn off excessive fuel.

  • sirthumpalot

Posted January 03, 2002 - 05:24 PM


Different bikes seem to have different solutions when it comes to fouled spark plugs, but for me and my '01 the answer was changing brands of gas. I was fouling one almost every time I started it while it was cold (first start of the day). I changed brands of gas and with no other changes at all I have not fouled a single plug since.

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  • Tom_Higdon

Posted January 04, 2002 - 02:36 AM


On my 01, the best thing I did was to start running a 50-50 mix of VP 108 octane and 92 octane pump gas and did the BK mod. Starts first kick EVERY TIME and have been on the same plug for 3 months now!

  • mikeolichney

Posted January 04, 2002 - 09:05 AM


These guys are right, the gas can cause this problem. The ethanol in the gas (madated near Denver in the winter) will foul my bike right away with a CR8E plug. A CR7E plug won't foul right away, but it sputters and runs poorly. Do not use gas with ethanol in it!

  • Merfman

Posted January 04, 2002 - 10:33 PM


Same story, different verse. A buddy of mine was having troubles with his '01 after the weather has turned chilly. Couple of weekends ago he decided to try 112 race gas and a 1 step leaner main jet. He reported a nice tan plug at the end of the day.

(Mike O, I tried to email you this but you might never have gotten it)


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