Featured 1971 T100c Refresh

Discussion in 'Vintage Classics' started by Sundance, Aug 6, 2022.

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  1. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    Iron, OK, I still haven't taken the ignition switch out of the circuit but was trying to trouble shoot in another way following some other advice.

    I used a voltmeter to check the battery before anything was turned on: 12.21

    After the ignition is turned on: 12.08

    Obviously I haven't ridden the bike much lately and it is not on a trickle charger.

    I was then going to find where the B-B Transistor box White Wire is connected to a bike White/Yellow wire, but they are pretty well covered and it looks like I will have to remove the gas tank to find this connection. So when I get a block of time where I can do this I will.

    A couple of other things, however. I can get the bike to start, and now it never runs nicely, always rough and variable. A bit of smoke too. While it was running I disconnected the left spark plug wire and it kept running at about the same pace. So I reconnected the wire and again, while it was still running, I disconnected the right spark plug wire and it kept running, roughly of course, but similar to when I disconnected the left plug. Might this be diagnostic of anything specific? Thanks!
     
  2. Iron

    Iron Elite Member

    Dec 29, 2021
    2,554
    943
    Bob Ross Studios
    Rough running and stopping on throttle use could be lack of fuel or lack of air and, of course, lack of electrickery when a connection disconnects with vibration.

    The original ignition switches are poo. I replace all the ignition switches on mine as a routine with modern switches. They are pretty easy to take out of the equation by joining the correct wires together. If your bike runs negative earth then join the positive wire from the battery (that runs to the ignition switch) to the ignition circuit wire (look up the correct wire on the circuit diagram). Positive earth will require the negative wire running to the ignition to be used.

    Check fuel delivery through the carb, tap etc using @speedrattle method with a measuring jug.

    Check that air can get to the carb by removing the air filter.

    Check that the pilot circuit in the carb is clear (this needs the carb to be removed and carefully checked and cleaned) you can do this easily yourself it just takes a bit of time. Look at this thread on how to do

    https://www.thetriumphforum.com/threads/t140v-amal-carbs-mk1.31915/#post-579003

    Take your time and slowly work through connections as you are doing, it'll work out and it's fun......sometimes :)
     
  3. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    OK, on my way. thanks!
     
  4. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    Electrical troubleshooting! I'm still having trouble troubleshooting my 1971, Triumph, T100C electrical issue. I checked the wiring of the Boyer-Brandsen MK IV and it looks to be properly appointed. As far as I can see it is getting juice. I made a YouTube video in case any members can take a look and help me a bit more with the diagnosis. Thanks if you'll take a look here:
     
  5. speedrattle

    speedrattle Senior Member

    Feb 19, 2021
    1,105
    243
    appalachia usa
    what exactly is the problem? i cant tell from the video.
     
  6. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    It seems to be only firing intermittently on each cylinder. The roughness you hear is that. I can still get it to run on either cylinder, but I think the spark is intermittent to each side. It used to run fine, then one day it started cutting out after a ride. Then I could ride it again for a bit till it started cutting out a bit, and I couldn't get it to rev up. I thought it was fueling so rebuild the carb but the problem remains. So it must be something electrical. I can get it to start and run a bit like in the video, but eventually it will not run. ? ?
     
  7. speedrattle

    speedrattle Senior Member

    Feb 19, 2021
    1,105
    243
    appalachia usa
    a boyer fires both sides at the same time. if it runs at all, then it should spark identically at both sides. so if the problem is on one side only. then the boyer is not at fault. look at plugs or plug wires.

    are you running 6 volt coils? a boyer runs best if you replace the 12 volt coils with 6 volt, but 6 volt should run better than what you videoes.

    i would guess carburation.

    put a timing light on the plug wire and see whether the spark is steady. if it is, then the problem is carburation. if it isn't, then look to coils, connections, plugs, or plug wires.
     
  8. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    OK, how about this? I am wondering if this is a different electrical problem or a carb problem. See the attached video of the plugs sparking when kicking the engine over. They seem consistent and uniform. Also, the plugs are wet when removing after running, so could this be a fueling issue and how would I troubleshoot this? https://www.youtube.com/shorts/C3Ui9Z6fVgQ
     
  9. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    I'm still trying to figure this out. So the bike starts easily, but still runs rough, like it is missing intermittently. When running I removed one the right spark plug wire and it kept running, but less firing. After connecting the right plug, I then removed the left, and it kept running, but just barely. So it would seem the left side is not running as smoothly as the right side. So could this be a left side coil or wiring issue that for some reason is not letting the left side spark as strongly as the right side? Thanks for advice!
     
  10. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    SR, I have 2x6volt coils. If you will see my latest post it seems one side is running better than the other. So I am wondering if it could be that one side, the left, coil is a problem and may not be firing as it should? Is this a possibility that a coil can still work but just not up to par? I suppose the only way to diagnose is to try another coil? Thanks for any ideas.
     
  11. darkman

    darkman Crème de la Crème

    Oct 26, 2015
    7,541
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    A low battery will cause a misfire and retarded ignition with Boyer ignition, had one the other day, fitted a new battery and problem gone.
     
    • Like Like x 1
  12. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    OK, I did make sure the battery was charged, having it on a tender and checked the voltage before doing this at 12.6. If this is the case could it still be the battery? Thanks
     
  13. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA

    ALSO - I tried switching coils. I ran the bike with the spark plugs wires switched to the other plugs - ran the same rough. Then I started and ran the bike on the right cylinder only, once with the left coil and once with the right coil. I did the same with the left cylinder. All four times it seemed to run the same, no missing just running on once cylinder. So I am wondering what this tells me . . . it seems that both coils are working OK? Also both spark plug wires seem to work ok, even on just one cylinder. So when I hook the plugs up normally, it is still running rough, so more than one cylinder is firing, just not evenly. Any advice?
     
  14. darkman

    darkman Crème de la Crème

    Oct 26, 2015
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    My friend said he had the battery tested on his Norton so i fitted a new battery on his bike and the problem was resolved, i would try a new battery :)
     
  15. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    Wow, OK. So the old battery tested OK for voltage, but still it was a new battery that fixed it? I will give this a try - because of this is the problem it is a lot easier fix than going thorough the who wiring bundle. Thanks.
     
    • Like Like x 1
  16. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    OK, so I have a 67 Bonneville with 12 volt battery and hooked this battery to my T100C. The same issue persists so the battery must be ok.
     
  17. darkman

    darkman Crème de la Crème

    Oct 26, 2015
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    Bummer, ok so if the 65 runs ok then try the 67 with the 65 spark plugs to eliminate them or a new set.
     
  18. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    OK, just now getting back to diagnose and fix this T100. So I went ahead and got new coils and plug and leads and installed them. Now, when trying to start, my ignition switch seems to be on the fritz! I'm not getting that red light coming on when turning the key on. Any thoughts on how to troubleshoot this? Thanks.
     
  19. Sundance

    Sundance Well-Known Member

    Aug 2, 2021
    217
    93
    Arlington, VA
    There is plenty of power at the battery and the coils, but no spark. Perhaps there is a way to bypass the ignition switch to see if it is the switch?
     
  20. darkman

    darkman Crème de la Crème

    Oct 26, 2015
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    A jumper wire from the battery to the neg feed on the coil will bypass the wiring, disconnect the white ignition feed wire from loom.
     
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