Aftermarket Pipes Backfire

Our Friends at SuperTrapp had this to say:
Do aftermarket pipes backfire? A backfire or “lean misfire” on deceleration is primarily attributed to an improperly tuned engine. Under this circumstance, the low speed fuel circuit needs to be adjusted. On a street bike, the rule of thumb is to adjust the fuel mixture screw out in ½ turn increments to add fuel. If you reach 3.5 turns out and it still pops on decel then go up one size on the pilot jet and turn the fuel mixture screw back to one turn out from bottomed.

Repeat this process until the misfire is eliminated. In some cases, this problem is an indication that the exhaust is too free flowing (ie. Head pipes too large in diameter or muffler core is too large) for the motor configuration you have. As always, check your spark plugs to verify the tune is correct. The plugs should be a light tan in color if tuned properly. If the exhaust is too “free flowing” you will ultimately add too much fuel which will cause an excessively rich condition and foul the plugs.

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24 Responses to “Aftermarket Pipes Backfire”
  1. Kerry

    I have a 2008 lowrider with slip on pipes sounds great but it pops when I let off the throttle, I was thinking the exhaust gasket may be leaking at the heads but the nuts are rusted bad I’m afraid to even tuch them. So what’s a good way to remove them without breaking them. That is one thing I don’t want to do. Thanks!

  2. Adam Lane
    Adam Lane

    I have an 06 Electra Glide Classic EFI with the same problem. I installed a set of S&S slip on mufflers and noticed the issue got worse. It popped with the stock exhaust as well. It has well over 60,000 miles could it be weak valve springs?

  3. Ian Welker
    Ian Welker

    I have a 2016 Breakout , with big radius Vance and Hines pipes. They pop on deceleration. They were already on the bike when I bought it from Longhorn in Grand Prairie Texas. What do I need to do to stop the popping ?

  4. Al

    Have a 01 road king with fuel injection new plugs sinthetic oil and and new air cleaner. Same little back fire on deceleration. The after market pipes are 2.25 inches. Would that require the map to be adjusted.

  5. Henry T.Kramer
    Henry T.Kramer

    I noticed you didn’t mention a possible exhaust leak. 9 out of 10 times in my experience, usually a leaky
    exhaust gasket will cause popping on deceleration. I assume it is due to a negative pressure in the pipe
    on deceleration that introduces oxygen into the pipe & ignites unburnt fuel in the exhaust.
    Also as a side note, a friend of mine said he had a hell of a time chasing a similar issue
    on a twin cam & found out it was due to sloppy cam timing. I think he said there was slop in the chain.
    I can’t personally vouch for that one, but I’ll keep it in mind if I run into the situation.

    • Edgewalker

      Ageed. I ride a ’85 FLHT Evo and replaced the stock duals with a Thunderheader 2 in 1. After about 10K, noticed a ‘chuff’ at acceleration and a pop pop at decel. Replaced the gasket, problem solved.

  6. Stephen Ginoulias
    Stephen Ginoulias

    On a Fuel injected engine, a backfire on deceleration would be caused by a possible what?

  7. Stephen

    I have a 2007 Softail Heritage Classic with Vanes & Hines pipes. About a month ago, I was riding home and my pipes started popping and backfiring. Also it felt like I had a loss of power as I could barely make it home. Now the bike won’t stay running. It turns over and starts for a few seconds and then dies, like it isn’t getting enough fuel. I have since replaced the fuel pump and fuel filter as well as new fuel. I have the same issue, cranks and stays running for a few seconds then cuts off. Any suggestions?

  8. Mancil

    I have a 1989 883 and had the carb cleaned and new tank installed but it backfires when I give it throstle it use to not do it I got it out of shop within week it ran good and has straight pipes and a super e carb

  9. Georgie Melendez
    Georgie Melendez

    I Had a big bore kit plus an after market Muffler installed in my 2017 Tao Tao Chinese ATM 50 A-1 gas scooter. So my muffler its backfiring when i Deccelerate.

  10. marint3

    Tell you what. Easy Peary. I purchased the FP3 and it works like a charm. It mapped my bike and if I decide to change other stock items I can map the new part(s) and it will tune my bike love new.

  11. CurtisKing

    Ticket 21860 Just had rear cylinder top end done, Bike is backfiring more than normal, I have drag pipes. Is there a fix for this?

  12. james mcIntyre
    james mcIntyre

    – I added v&h slip ons on my 2015 fatboy it backfires so Harley dealer did a stage 1 screaming eagle and it still backfires. What can I do?