XR650R Backfiring


Just given the above a major service - new plug, valve clearances etc. At the same time removed an IMS tank and put a rubber pipe from the now defunct vacuum take-off and plugged the other end with a bolt.

However, the bike now starts but backfires when idling and when I close the throttle. It didn't before.

Any suggestions?



sounds like a vacuum leak.

If that's all you did, then it's probably something you changed or did.

you can use the smoke test to see if you have a vacuum leak at one of those connections. I always have to borrow a cigarette, as I don't smoke, but it works pretty good. You'll see the smoke get sucked in the vacuum leak when you find it.


or carb cleaner sprayed around the area will cause the revs to rise if it enters the intake.

Gotta think on this one a little more though as my bike is apart right now and has to be back together tonight to race tommorrow, better hit the garage, good luck.

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