1998 yz400

3 replies to this topic
  • ironmanyz400

Posted December 02, 2009 - 08:53 AM


Hello. Just bought the bike it runs well but when it gets to the upper rpms it acts like a governor is restricting it. I asked Yamaha about it they said they do have rev restrictors but it seems to be kicking in too early or its something else. Looking for some direction. thx.

  • grayracer513

Posted December 02, 2009 - 09:20 AM


If your air filter is clean, and the exhaust not restricted, check for a short in the light blue lead that runs between the neutral switch and the CDI. This is the neutral signal lead, and the neutral switch is supposed to ground it when the bike is in neutral, but not at any other time. If it gets grounded, one of the things that is supposed to happen is that the rev limit will be reduced from 11,500 to 7000 rpm. 7K is right in the meat of the power peak, so you would notice that right away.

Dirt or water in the carb is another possibility.

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  • jcm3

Posted December 02, 2009 - 10:22 AM


Dirt or water in the carb is another possibility.

Yeah, I was thinking gummed up main jet possibly. I just bought a 2001 YZ426, and when I test rode it it would bog down and stall if I gunned it.

A quick clean out of the main jet and I was off and running.

  • ironmanyz400

Posted December 03, 2009 - 02:25 AM


Thanks for the input. i'll check it out.

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