Causes and Cures for Popping on Deceleration

There’s a lot of discussion about popping on deceleration. I have this problem myself. What are the most common causes and cures for this problem on a fuel injected twin cam motorcycle?

From Our Friends at DynoJet

Popping on deceleration is due to unburnt fuel being ignited in the exhaust. The reason you do not hear this on a bike with a stock exhaust is due to the baffling of the stock exhaust. It is not only much quieter but also does not allow the fresh air to enter the exhaust due to reversion. This fresh air makes the exhaust hotter (think of letting a fire have more oxygen) which aids in the combustion of the unburnt fuel.

To REDUCE (it may not totally go away) popping on deceleration first make sure that you do not have any intake or exhaust leaks. If all that checks out then you can alter the fuel curve at closed throttle to help this problem. If you are using a PCIII then go into the 0% column of the software and alter the fuel curve from 1750-5500rpm. The value you enter depends on your model and setup. Some Magnetti Marelli bikes responded by having a -60 put in this column while most Delphi bikes respond by inputting a +25. Also make sure that you synch the Throttle Position so that it reads 0 while the bike is idling.

Wrench Safe, FMH
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17 Responses to “Causes and Cures for Popping on Deceleration”
  1. TREVOR

    I have a 2009 sportster 1200 (XL1200L). Recently upgraded to V&H slash slip-ons. I still have the stock intake in place. No reflash or upgrade to ECM. On decel or downshifting I get a lot of popping from the exhaust.
    My question is if I install the heavy breather intake from screamin eagle and upgrade the fuel map would that improve the performance and get rid of the popping on decel/downshifting?
    Any suggestions would be appreciated. Please advise…

    Reply
    • driveshaft

      Check neck bearings for grease and loosness..they may need repacked or replaced also check slider bushes for play in lower legs as this can cause same effect when traveling slowly on bumpy roads..its usally the beck bearings..one other thing to check is brake caliber to make sure it isn’t loose on the slides..first thing to do for all these things is to get a good jack like an atv jack that will lift the whole bike off ground..then check each place for play or loosness..to check the lower legs it will be necessary to remove the front wheel so each side can be checked and also that no heavy load from wheel and tire fools you into thinking they are ok..

      Reply
  2. Dave Pike

    I own a 2006 Harley-Davidson Deluxe which is beautiful. My local HD staff gave me the excuse that back-firing when deaccelerating is normal for a cruiser and stated that all cruisers do this some. Your opinion, please.

    Reply
  3. Tim

    My 07 Ultra Classic has a Power Commander with true duels and O2 sensor bypass harness and have the same exhaust pop. Sometimes in the summer it’s so loud I look back to see if I blew off one of the Rinehart muffers. Bought this bike used in 2010 and don’t have the disk or any harness needed to interface with the Power Commander.

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  4. Keith

    I guess I am just an old rebel because I like the pop and crack of the exhaust when I back off or let engine hold back speed coming down a mountain road.

    Reply
  5. George d

    I had the same problem. I added a fuel controller to add fuel and it never back fired again. I had 12 heritage 103 that ran so lean and hot i used more fuel to cool it down. It worked great.

    Reply
    • Sandy

      @George d is it just called fuel controller or can it be called something else I’m not finding anything called that where I live. Thanks

      Reply
  6. michael hyatt

    I have a 2006 Harley Davidson Street Glide with stock 88″ motor. I have installed Rinehart true duals with 4″ Rinehart slip ons. I installed Vance and Hines led fuel pak.I have replaced exhaust gaskets twice. Tightened muffler clamps. Removed injection module and intake. Replaced all orings along with injectors. I have tried several different maps recommended by Vance and Hines. Nothing ever seems to help the pop I get through left side (rear cylinder) exhaust on decel. The pop begins at 1600 rpms and is rear cylinder only. Any ideas?

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