T140v Rough Running - Left Side Missing

Discussion in 'Triumph General Discussion' started by MartinUK, Nov 16, 2025.

  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  1. MartinUK

    MartinUK New Member

    Nov 16, 2025
    2
    3
    UK
    I've just got a 76 T140V. The previous owner said he had refurbed the carbs but on the ride home it was missing and would not rev smoothly. Today at home I could only start it using easy start. Once warm the left side is missing and rough running together with some blue/grey smoke out of the exhaust. I swapped the plug leads and it's still the left side that is rough. I can also see that smoke is leaking out of the front of the left cylinder, where the exhaust goes in, not much and only really evident when I try to rev it. So, is this a carb issue?
    If I put a new plug in the left side it will run OK for a few minutes but then starts the problem again. If I take out that plug it is wet. The bike has wassell electronic ignition. The carbs are the Amal type with a tickler but also have a choke slider with a lever on the left side.
     
    • Useful Useful x 1
  2. TRIPLE X

    TRIPLE X Senior Member

    Sep 1, 2021
    684
    243
    Norfolk
    It might be worth swapping the coils over to rule out a defective coil on the left side?
     
    • Like Like x 1
  3. MartinUK

    MartinUK New Member

    Nov 16, 2025
    2
    3
    UK
    Thanks, gonna try that but I've already swapped the plug leads so that also means all the circuit up to there swaps too(including coils).
     
    • Agree Agree x 1
  4. Romeo Keller

    Romeo Keller New Member

    Oct 18, 2025
    0
    1
    Switzerland
    I think this is an oil-problem. Pistonrings or valveguides worn. So you have to strip the cylinderhead and find the problem. Regards from Switzerland
     
    • Useful Useful x 1
  5. TRIPLE X

    TRIPLE X Senior Member

    Sep 1, 2021
    684
    243
    Norfolk
    Yes, it does appear to be burning oil hence the blue smoke. Might be worth doing a compression test before stripping it down to see if there is a significant difference between cylinders.
     
    • Agree Agree x 1
  6. Mike_Oxmall

    Mike_Oxmall New Member

    Jun 18, 2025
    19
    3
    Nr Scunthorpe
    #6 Mike_Oxmall, Nov 17, 2025
    Last edited: Nov 17, 2025
    Is the choke opening on the left carb. I never had choke sliders in on my 120V.

    Take the choke sliders out. You don't need them. Just a good tickle and she should start perfectly.

    Are the slow running jets set at 1 1/4 -1 1/2 turns out.

    I had a "Gunson" colour tune years ago and you could set the slow running perfect with it.

    Is the left needle in the correct position height wise.

    Worst case. . . swap the carbs over and see what she runs like.

    Inlet manifold may be cracked or bad gasket.
     
    • Agree Agree x 1
  7. TRIPLE X

    TRIPLE X Senior Member

    Sep 1, 2021
    684
    243
    Norfolk
    If it has electronic ignition the condensers should have been ditched?
     
    • Agree Agree x 1
  8. Mike_Oxmall

    Mike_Oxmall New Member

    Jun 18, 2025
    19
    3
    Nr Scunthorpe

    Correct. I'm doing 3 things at once and just ran through my thoughts forgetting he had EI fitted.

    So we're back to carbs. Inlet manifold may be cracked or bad gasket.
     
    • Like Like x 1
    • Agree Agree x 1
  9. Iceman

    Iceman Crème de la Crème

    Apr 19, 2020
    2,959
    1,000
    Lancashire
    I would undertake a compression test first, however, given that you say it emits blue/grey smoke it is a strong indication of burning oil. It will need the head and barrels removing to inspect. Don't run it anymore, if a ring is broken it can cause further damage.
     
    • Like Like x 2
Loading...

Share This Page