Bonneville T100 Afterfire When Deceleration

Discussion in 'Technical Help' started by Guillermo salinas, Aug 25, 2019.

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  1. Guillermo salinas

    Guillermo salinas Well-Known Member

    Aug 17, 2019
    161
    93
    Azusa
    My Bonneville T100 is after firing or backfiring when downshift. Any suggestions as to the cause and fix?
     
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  2. sprintdave

    sprintdave Nurse,he's out of bed again

    May 25, 2014
    1,495
    750
    Birmingham
    Air leak at header pipes?
     
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  3. joe mc donald

    Subscriber

    Dec 26, 2014
    13,923
    1,000
    slough / burnham
    Guillermo Salina
    What pipes are you running and have you disconnected anything like the induction kit on the head to airbox. And a lot of aftermarket exhausts do pop a bit on over run. I quite like it if it is mild. If not happy get it remapped and set up for any items disconnected. Would not worry to much as it is only unspent fuel in the exhaust system.
    Regards
    Joe.
     
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  4. crispey

    crispey crispey creme de la creme

    Nov 6, 2014
    7,198
    1,000
    Uk
    If you’ve put after market pipes on try disabling sai, you can do a quick test by removing the rubber pipe from the air box and blocking the pipe with a marble or cork.
     
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  5. Guillermo salinas

    Guillermo salinas Well-Known Member

    Aug 17, 2019
    161
    93
    Azusa
    They are the stock pipes and I have made no changes. I noticed the left pipe has a little play and can be wiggled a bit.
     
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  6. Guillermo salinas

    Guillermo salinas Well-Known Member

    Aug 17, 2019
    161
    93
    Azusa
    I don't know much about motorcycle so I don't understand all the suggestions. Take a look at the Gap in connecting the exhaust pipe. I tried to reduce the space but I'm unable to do so based on where the rear foot peg is. I've tighten the clamp but there still some play in the pipe. I don't want to over tightened and crimp the pipe. 20190825_110104.jpg
     
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  7. sprintdave

    sprintdave Nurse,he's out of bed again

    May 25, 2014
    1,495
    750
    Birmingham
    If you mean there is play between the silencer and downpipe in the uk you can buy a paste called gun gun which you smear into the join then tighten the clamp and run the engine to harden .
    Also I meant a leak at the top of the downpipe where it connects to the head, can you hear any air sound there if you rev the throttle.
    Is the bike new, I think not ? But if so return to dealer to sort.
    These fixes are based on older bikes, not sure about yours but dont see why not.
     
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  8. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
    800
    Nr Biggar
    Has it already been over tightened? It looks like the bolt head might have pulled through the exhaust clamp.
     
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  9. feckless

    feckless Noble Member

    Apr 16, 2019
    1,027
    443
    Cumbria
    just remove the silencer and put a light smear of silicone sealant around the edge that connects to the header pipe.
    I find silicone is much better than gun gum as it does not harden and crack
     
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  10. Vectis John

    Vectis John Well-Known Member

    Apr 17, 2019
    88
    68
    Isle of Wight
    #10 Vectis John, Aug 30, 2019
    Last edited: Aug 30, 2019
    I have a totally standard 2019 T100 and it is prone to a little popping on overrun. (I quite like it!)
     
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  11. Guillermo salinas

    Guillermo salinas Well-Known Member

    Aug 17, 2019
    161
    93
    Azusa
    Sorry that was a picture without the bolt on.
     
  12. Guillermo salinas

    Guillermo salinas Well-Known Member

    Aug 17, 2019
    161
    93
    Azusa
    Sorry that was a picture without the bolt on.
    I guess I'll enjoy the popping myself given it's not a big problem. Thank you all.
     
  13. Callumity

    Callumity Elite Member

    Feb 25, 2017
    3,358
    800
    Nr Biggar
    Yes, the bolt was obviously missing but the clamp looks damaged!!
     
  14. SpeedTwin1200

    SpeedTwin1200 Senior Member

    Jul 21, 2019
    261
    113
    Hampshire
  15. Guillermo salinas

    Guillermo salinas Well-Known Member

    Aug 17, 2019
    161
    93
    Azusa
  16. Guillermo salinas

    Guillermo salinas Well-Known Member

    Aug 17, 2019
    161
    93
    Azusa
  17. Guillermo salinas

    Guillermo salinas Well-Known Member

    Aug 17, 2019
    161
    93
    Azusa
    Here are two better pictures.

    20190903_011756.jpg

    20190903_011734.jpg
     
  18. Duffers

    Duffers New Member

    Jul 11, 2022
    0
    1
    Surrey
    Same thing happened to me , can anybody point me as to where I can get new bracket etc Ta
     
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