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Shimmed valves, gnarly backfire

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     Been doing some searching, can't find quite the same scenario. Apologies if this is beating a dead horse. 

      Just re-shimmed my valves today, brought back into within a 0.001 of factory. Starts instantly, idles fine but backfires hard on decel (shoots a flame out the pipe). Ran perfect before this, just started to get a little grumpy about starting at the beginning of the day.

      '09, un-corked, jetted for local elevation (as per JD instruction), smog delete

      Did not change anything on the bike at this time but did remove and reinstall the header pipe to remove a dent. (Side note: water in the pipe and a night in the freezer works pretty well.)

     Wondering if I may have ended up at tooth off on cam timing or screwed up something while messing with the pipe?

     Thanks for your time and input.

     

     

      

Edited by Murphy204
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 I'd loosen up the muffler, mid-section connection, and head pipe, then tighten back up in reverse.   You may have a air leak at the head.

 If that doesn't change anything, then pull the valve cover, check the lash again, cam timing, and that the auto decompression is working as it should (weights should move freely in and out, and pin should stick up and drop down).

Jim.

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