Backfireing when decelerating

Preventing Backfire on Motorcycle Exhausts ' DoItYourself ...

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When the engine on your motorcycle has an emission system malfunction, such as anexhaust leak or a moment of running rich or running lean, backfire can ...

Exhaust backfire, popping when letting off throttle - Motorcycle Forum

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Apr 26, 2009 - 28 posts - ‎17 authors
Exhaust backfire, popping when letting off throttle General Motorcycle Discussion. ...You can damage the engine by running too lean or rich. Backfires on deceleration
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Jun 12, 2010 - A visible flame may momentarily shoot out of the exhaust pipe. ...Another backfire situation occurs when the engine is running rich, meaning ...

Is backfire when decelerating a bad thing? : motorcycles

Charlene: According to https://www.briggsandstratton.com/us/en/support/faqs/engine-backfire-afterfire " What causes a small engine backfire & how do I fix it? Backfire typically occurs when the engine is decelerated rapidly.

Common Causes of Backfire:

• Lowering engine speed too fast
• Gasoline, which contains higher blends of alcohol
• Carburetor adjustment set too lean
• Muffler construction can induce backfire
• Higher than normal engine temperatures
• Some carburetors can induce backfire due to the sensitivity of internal transitional passages
  (This condition cannot be corrected).

Possible Fixes for Backfiring:

• Lower engine speed slowly
• Follow small engine fuel recommendations and/or switch to brands with low or no alcohol
• Adjust carburetor for optimum performance
• Inquire with equipment manufacturer about increasing air volume to decrease engine temperature"

Charlene: I hope that helps! :)
Charlen

BACKFIRE OCCURES DUE TO RUNNING TO RICH AND EXPELLED UNBURNED RAW FUEL EXPLODING IN TAIL PIPE.WHEN COOL AIR HITS IT FROM DECELERATION THE ENGINES SUCKING IN MORE AIR CAUSING IT..A LITTLE BACKFIRE IS NOTHING TO WORRIE ABOUT IF ITS A CANNON GOING OFF YOU NEED TO ADDRESS IT..THE FUEL TO AIR MIXTURE ISNT CORRECT..I WOULD LEAN IT OUT ALITTLE.

Aftermarket pipes tend to lower back pressure, this will cause the fuel/air mix to lean out and result in the "popping" you hear---Backfiring, is extremely rare these days with electronic ignitions and the high reliability of engines. Real backfiring means the engine is not properly timed and the fuel/air mix is getting a spark and ignition at the wrong time (when the intake valve is open). Real backfiring is actually the bike "spitting up" in a sense, backwards through the carburetor or intake.You can check for exhaust leaks up around the cylinder heads by putting on some gloves and covering the exhaust tips momentarily. I have seen exhaust leaks that will make the popping worse by allowing air to be sucked in during deceleration...Hope this helps.

Backfiring can be caused by fouled spark plugs (you have four,two per cylinder), bad spark plug caps, bad air cut valves on the side of the carburetors, but most likely leaking exhaust gaskets. I am guessing that you have changed the exhaust system but did not put new crush o-rings between the cylinder head and the head pipe. You should also change the tubular gasket/seals between the head pipes and the mufflers. If this does not fix the problem , take out the two screws that hold the air cut diaphragms in place and remove the covers . If the rubber diaphragms have holes in them or have become sticky they need to be replaced. Air cut diaphragms turn off the fuel during deceleration to prevent back firing. If they go bad they can cause poor running , popping , and back firing during normal operation.

The most common reason for backfiring is lack of back pressure from changing the exhaust. To compensate for the flat spot you get you put in a jet kit. This leaves the possibility of more unburned gas getting into the exhaust. Honda uses Kei Hin carbs with a fuel shut off diaphragm to help limit this condition (backfiring) by turning off the fuel to the carbs during deceleration. Even stock exhaust can pop or backfire. Typically it is caused by air getting into the exhaust either past the copper o-ring gaskets in the head or leaking muffler connections from the head pipes to the mufflers. Try replacing all the exhaust gaskets and you should minimize this condition.

Have you tried new spark plugs? One fouled plug or bad spark plug cap can cause backfiring. Possibly dirty carbs ( a stuck float). Backfiring on deceleration can be caused by bad exhaust gaskets where the headers attach to the head (an air leak)

Backfiring during deceleration is caused by even small leaks in the headpipe and/or rich carburetion. I suggest checking your pipe for leaks and look into your jetting.

Some occassional backfiring is typical.