Misfire on 73 Bonnie

Discussion in 'Technical Help' started by Tigertodd73, Aug 25, 2016.

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  1. Tigertodd73

    Tigertodd73 Member

    Jun 10, 2016
    9
    8
    Kilmarnock
    Hi all. Put post up a few months back. Having trouble with the auld 73 t140v. I got brand new wassell carbs and had to send one back for being faulty. Replacement was alot better but bike still is not running 100%. Bike would always start first kick but now it is a nightmare to start, once i get it going and go a run, it starts no problem from then on. Ive had problems with the right side and it is back to misfiring quite bad, ive tried adjusting carb and just cant get it to settle down. Both carbs are set the exact same, left side perfect, right side awful. All electronics have been checked by a trusted and respected auto electrician who has a love of bonnies for many a year. What am i missing??

    Cheers
    Tiger
     
  2. TEZ 217

    TEZ 217 Crème de la Crème

    Mar 6, 2016
    3,148
    1,000
    south shields
    As for the carbs - which side was the one you sent back ? left by chance !! (could you not have received two duff one's from the start)
     
  3. Tigertodd73

    Tigertodd73 Member

    Jun 10, 2016
    9
    8
    Kilmarnock
    Was the right one, and its still right side thats not running right. It seems that when i shut off the fuel it runs better, then have to put fuel back on obviously.
     
  4. TEZ 217

    TEZ 217 Crème de la Crème

    Mar 6, 2016
    3,148
    1,000
    south shields
    Could be over fueling ? sticking carb float or wrongly adjusted,
    just throwing out a few ideas, I'm sure others on here will help more when they see your post
     
  5. darkman

    darkman Crème de la Crème

    Oct 26, 2015
    7,535
    1,000
    Southcoast of the UK Earth
    Have you set the float levels
     
  6. Tigertodd73

    Tigertodd73 Member

    Jun 10, 2016
    9
    8
    Kilmarnock
    Float levels are exactly the same both sides. This is the third carb (original amal, new wassel, replacement wassel)
    I will check the levels again but im sure they are exactly the same.
     
  7. Tigertodd73

    Tigertodd73 Member

    Jun 10, 2016
    9
    8
    Kilmarnock
    Someone mentioned intake valve?? What should the valves be set at? Been told 1 thou?
     
  8. darkman

    darkman Crème de la Crème

    Oct 26, 2015
    7,535
    1,000
    Southcoast of the UK Earth
    Factory says 2 n 4 thou but 3 inlet and 5 ex work better :) Floats should be 5mm down from top of bowl
     
  9. camman

    camman Member

    Jun 7, 2015
    19
    8
    christchurch dorset
    What ignition system do you have, old points system?...old Lucas E.I.?...or Boyer. or Pazon E.I.?
    If old points system, it could be a faulty capacitor or the right side points are shorting to earth or cable going O.C. (sometimes the flexi cable that fixes to moving point breaks down with fatigue).
    If you have old Lucas E.I. the control units have a habit of "drifting"
    With a Boyer or Pazon fitted timing will be correct on both cylinders, as it works on "lost spark" principle, and of course there are no capacitors.
    With the points system you have possible slight variations in timing due to points gap and points positioning.
    If you do have points and capacitors, the first thing I would do is swap the capacitors to see if it transfers the fault to other bore, as you did with carbs.
    Graham
     
  10. Taff Salmon

    Taff Salmon Active Member

    Aug 22, 2016
    77
    28
    no
    "Wassell" could be your problem. They supply pattern parts.
    Always get your carbs direct from Amal or from Surrey Cycles.
    Valve clearances should be 2 and 4 thou.
     
  11. Taff Salmon

    Taff Salmon Active Member

    Aug 22, 2016
    77
    28
    no
    Also look up the Amal website. It tells you how to set the float height correctly by moving the brass float needle seat in the float bowl. 5mm is too low.
     
  12. camman

    camman Member

    Jun 7, 2015
    19
    8
    christchurch dorset
    The reason I am suspecting ignition as opposed to carbs is, I had the same symptoms on a 1980 T140E with Lucas E.I.
    It turned out to be "drifting" on the timing and also had a faulty capacitor.
    Fitted Pazon E.I. and dual outlet coil, and it now runs as smooth as a smooth thing all the time:)
     
  13. camman

    camman Member

    Jun 7, 2015
    19
    8
    christchurch dorset
    But...also agree it could be float levels or float level cut off needle/seat leaking....which would account for it running better when you turn fuel off for a while.
     
  14. Tigertodd73

    Tigertodd73 Member

    Jun 10, 2016
    9
    8
    Kilmarnock
    Hi folks. Got to the bottom of the problem. Timing was out. Sorted that then set the carbs. Right carb was alot more responsive while adjusting this time. Bike is running a hell of alot better.

    Have noticed my clutch is slipping though so gony get new clutch plates and pads. Is there a specific set to get as my clutch is belt drive?

    Thanks for all the help.
    Tiger
     
    • Like Like x 1
  15. darkman

    darkman Crème de la Crème

    Oct 26, 2015
    7,535
    1,000
    Southcoast of the UK Earth
    Just make sure that after you have fitted the clutch you turn the engine over and adjust the springs so as the clutch unit is not wobbly, remove cable from bar end and then slacken off lock nut, screw in adjuster rod until plate lifts, back off a little and tighten nut.
     
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