WR400F blue smoke?

4 replies to this topic
  • cmwr250

Posted May 04, 2011 - 07:32 PM


I bought a 99 wr400f two weeks ago. the guy said it had top end rebuilt last summer. Ran good with no smoke untill today. started it up and rode it a little while and it started making a ticking/slapping sound. i could not tell if it was top or bottom end. i let it sit awhile and started it up again. blue smoke rolled out of the pipe and just smoked horribly.
i tore it apart tonight.valves were in spec. oil was all over in combustion chamber. no broken rings. piston has no cracks. i have not taken the valves out yet. Is it possible that a valve seat is cracked in the head? wat could cause it to smoke so suddenly and i am sure i dont have a broken ring. im 17 and dont really what im doing. Any help would be appreciated thanks

  • woods-rider

Posted May 04, 2011 - 07:43 PM


Blue smoke typically indicates burning oil.

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  • cmwr250

Posted May 05, 2011 - 04:29 AM


yes but could oil seep through if i had a cracked valve seat in the head?

  • shelbyguy

Posted May 08, 2011 - 09:58 PM


valve stem seals, or broken piston ring?

  • William1

Posted May 09, 2011 - 03:09 AM


You bought a '99 wr that the owner states 'just had a new top end'. Every bike for sale has a 'new top end'. I also have a bridge for sale and you have a very beautiful baby...

Check the crank and rod for any sign of vertical play. If there is any, it needs to be serviced too.
You will want to get the barrel replated, a new piston and rings. Will not hurt to have the valves done.
This can cost $600 to $1,000 but you will actually have a fresh top end.
A good shop can easily check for head cracks.


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