wr400 NEED HELP

[kieran 400wr]

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]

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

[dgcars]

+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.

[kieran 400wr]

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]

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]

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

[gjscott]

Maybe an inlet vacuum leak. That can cause backfiring.