98 yz400f motor done?

5 replies to this topic
  • rickmancc

Posted May 20, 2008 - 01:28 PM


I have a 1998 yz400 f I just picked up not running, I found the oil is gray and the anti freeze low, also the exhaust was full of black gas. I searched the forum and looks like I have a grenaded motor, has anyone run into this?

  • 426 NOOB

Posted May 20, 2008 - 02:19 PM


To me it doesnt sound like the motor is blown, but instead, these are all signs of a blown head gasket, aside from the black gas. Coolant in the oil is a head gasket prob. If I were you, I would tear the motor down and replace the base and head gasket. And while your in there replace the cam chain and look for any other worn parts to replace. Hope this helps.

  • Twistedtrik

Posted May 20, 2008 - 06:14 PM


Also check your water pump seals. I drained my whole cooling system into the oil in less than 4 minutes of running. Both seals were gone and the water pump impeller shaft had a groove in it. I was told that water in the oil due to the WP seals was not likely, but it was what caused it. Just an idea.

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  • mjw1

Posted May 20, 2008 - 07:02 PM


i own a yzf 400 check the compression if that is good look for a blown head gasket but it should still run if it has a blown gasket. next clean the pilot jet these bikes the pilot jet plugs up real easy.

  • rickmancc

Posted May 20, 2008 - 07:52 PM


I will try that how can i post pics on here? sorry nub

  • grayracer513

Posted May 20, 2008 - 08:06 PM


open a free account at photobucket, etc., then link them here.

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