Running On Two

Discussion in 'Thunderbird' started by David H, Jun 9, 2025.

  1. David H

    David H New Member

    Aug 16, 2017
    1
    3
    Hull
    Out on the bike toady for a ride all went well had to go to reserve then filled up, no probs stopped for tea then set off back been running for 20miles or so when backfire from one side and bikes running on two cyls and cutting in and out of three, first thought bit of muck in fuel but then wondered about coils, still on old ones, what would be the symptoms of a coil breaking down?
     
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  2. David H

    David H New Member

    Aug 16, 2017
    1
    3
    Hull
    How do i get hold of Paul Messenger to order a set of stick coils ?
     
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  3. joe mc donald

    Subscriber

    Dec 26, 2014
    15,601
    1,000
    slough / burnham
    @David H Welcome to the family.
     
  4. David H

    David H New Member

    Aug 16, 2017
    1
    3
    Hull
    Further to my saga "running on Two" I have now replaced the coils and spark plugs, drained the tank and cleaned it out, had the carbs off and given them a clean up made sure all the connections are sound so time for a ride out!!
    First 10/15 miles all sweetness and light then the occasional miss mainly when accelerating, not as bad as it was , when cruising the bike seems ok but throttle back for a roundabout and start to accelerate it goes down onto two and coughs and splutters before picking up. im loath to take it to a garage as its going to cost a fortune for them to even find the cause.
    Any suggestion as to what to try next invited
     
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  5. Boothman

    Boothman Elite Member

    Jul 26, 2023
    1,027
    800
    Wigan
    Sounds like you can discount a spark issue unless the ECU is having issues - have you had it checked for any stored error codes?

    So that leaves an insufficient air or fuel problem. Does it misbehave if you run it up through the gears on the centre stand? If it does then I’d be tempted to remove the air filter and see if that rectifies things.

    if it does you need to look for a restriction in the air flow. If not then looks like it’s a fuel flow restriction.
     
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  6. TRIPLE X

    TRIPLE X Senior Member

    Sep 1, 2021
    669
    243
    Norfolk
    Is the fuel tank venting OK. Check for vacuum in the tank. Open the cap and see if it hisses.
     
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  7. Pegscraper

    Pegscraper Elite Member

    Jun 12, 2020
    3,783
    800
    Yorkshire
    How did the old plugs read, did they all look the same?
     
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  8. Eldon

    Eldon Crème de la Crème

    Nov 14, 2018
    8,915
    1,000
    North Yorkshire
    Is it always the same cylinder that misfires, or is it random?
    Is it heat related i.e. hot engine only, or it can be either hot or cold?
    When was the valve clearances last checked?
     
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