Fouling Plugs

6 replies to this topic
  • Descendents

Posted August 15, 2005 - 11:39 AM


I have a 2002 yam 426 with JD Jetting. Tried blue#4, Red #5 and still after a couple of rides plug fouls. Anybody have any problems with there plugs fouling? I ride in Mi around 1000ft. I'm getting tired of changing the plug, its not like the old air cooled fourstroke that took 2 minutes to change, then again my old suzuki dr 350 never fouled a plug. Any suggestions will be appreciated. Thanks

  • Matty05

Posted August 15, 2005 - 03:19 PM


you are way to rich..............

  • yamahazinger

Posted August 15, 2005 - 05:24 PM


u must have jetted it to rich. go back to stock jetting and go from there, or swap out one jet at a time and see what the difference is

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  • 02YZ426

Posted August 15, 2005 - 05:37 PM


Try the stock jetting and a new plug and see what happens... if its still fouling up plugs maybe try leaning the needle one position, Thats what worked for mine anyway.

  • Gadsen

Posted August 15, 2005 - 08:44 PM


Use the 165 or 168 main jet, blue #3 and fuel screw set at about .75 to 1 turn out. Its a little fat on the fuel dude! I ride about the same levels, but on a 450, and have found this set up to be good.

  • Descendents

Posted August 16, 2005 - 12:29 PM


Thanks, the next time I ride I will try blue #3 and red #4 with a 168mj. Hopefully that will cure the plug problem.

  • Joe Reitman

Posted August 16, 2005 - 12:58 PM


Often the pilot jet is too rich and the main cause of fouling. Needle is primarily 1/4 to 3/4 throttle and main is mostly WFO. Thus unless you are a desert racer wide open all the time fouling is typically from over rich slow speed circuit, not the main and typically not the needle. YMMV :D


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