6 replies to this topic
  • kieran 400wr

Posted July 22, 2011 - 01:22 AM


hi my 00 wr400 has run good for the past 2 years but now has started to back fire when im slowing down a lot , it has stop idle as well and is very hard to start . it runs good when driving at hi rpm but not so good at low . any ideas

  • board9898

Posted July 22, 2011 - 01:29 AM


Sounds like a blocked pilot jet or dirt in the fuel bowl.

  • dgcars

Posted July 22, 2011 - 01:50 AM


+1 on the PJ. You should have a 45# or thereabouts in there. Either take it out and clean or if it were me, i'd pop a new one in there.
A problem with WR's.....go forever.
Check the valve clearances to keep everything tip-top. If the popping on decel persists, make sure you there are no leaks around the header.

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  • kieran 400wr

Posted July 22, 2011 - 02:07 AM


thanks lads ill try that i was told it could be timeing chain so was geting worried there ill let u know if it works
.i put it up for sale and the day after it starts this i dont think it wants to go , THANKS LADS

  • board9898

Posted July 23, 2011 - 12:35 AM


Almost certainly nothing to do with the timing chain. I had a WR400 for two years with a rattling timing chain and it still ran fine. Unless it has jumped a tooth, but it doesn't sound like that from the symptoms you describe.

  • KevB

Posted July 25, 2011 - 06:20 AM


If it's not that Jet, my money's on one of the Exhaust vavles getting tight... check the valve clearances.

  • gjscott

Posted July 25, 2011 - 03:08 PM


Maybe an inlet vacuum leak. That can cause backfiring.


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