How do you measure spark?

Discussion in 'Tech Area' started by Jeff N, May 11, 2021.

  1. Jeff N

    Jeff N New Member

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    I am continuing restoration on 2 CT70's. The yellow is an H1 and the blue is H2. I have replaced the whole electrical system since everything is 50 years old. I installed OHTOKC electronic ignition, new coil, new battery, new harness. I get a good spark when testing with jumper from OHTOKC ignition plug to ground.
    A weaker looking spark at sparkplug when using a jumper wire from OHTOKC ignition plug to black coil wire. I have limited abilities with voltmeter but I am learning everyday. Please let me know how to measure the spark and what a good reading would be. Thanks for the help.
     
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  3. OLD CT

    OLD CT Well-Known Member

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    Oh! You have spark? You never finalized the other thread, ''no spark'' you opened. It helps other members when they search on here for similar problems and how you fixed it.
     
  4. lukelaw1

    lukelaw1 Active Member

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    Don't test spark with a volt meter, most aren't rated for that much voltage and will ruin the meter or blow the fuse in the meter.

    I'm a little lost in your details. everything is installed and you are just connecting at different points with a jumper?
     
  5. Jeff N

    Jeff N New Member

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    I have spark but it is so weak it is hard to see. Do you know how to measure the spark?
     
  6. Jeff N

    Jeff N New Member

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    I have spark from CDI ignition stator black wire when i ground it
    I have a weak spark at spark plug when I use a jumper wire from black wire of CDI ignition stator to black wire going into coil
    I have no spark at spark plug when everything is connected.
     
    #5 Jeff N, May 12, 2021
    Last edited: May 12, 2021
  7. TNtinker

    TNtinker New Member

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    I am having about the same problem. I have a 1972 CT70 was running but had to have the choke partially on. I bought a new carb from CHP and put it on started it for a couple of minutes then it died. I could not get it started again so i pulled the plug and no spark. I should mention that it had been spliced up and wasn't running when I got it so I bought a new wiring harness and switch and put it in. I think I have it wired correctly as all lights in speedo were working, break lights were working as well as head light and it was running all be it not perfectly. I am not good with meters, volts, ohms, and the like but can handle a tester light. When I couldn't get a spark I replaced the spark plug and just started moving up the line. I put a new coil on it and no spark, rebuilding the stator seemed to be to many things I could do wrong and not get spark so I put in the CDI ignition instead and put it in yesterday and hooked it all up. Turned the key on my green neutral light was on I laid the spark plug against the engine and turned it over and no spark and my green neutral light went out and isn't burning now. I went inside pulled my hair out and said some choice words then joined this site hoping for some guidance.
     
  8. Jeff N

    Jeff N New Member

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    I have been away from the CT70's for awhile due to work. Did you ever fix your problem?
     
  9. OLD CT

    OLD CT Well-Known Member

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    TNtinker, You need someone like another member here that lives close by to look at the bike... Too much stuff changed at once will do it. There is a long list of stuff you did or didn't do, that could be a problem... My crystal ball is empty.
    Here is what I do know...
    Coils never go bad unless it's too short from cutting it or the wire is hard brittle cracked and broken... That was a waste, buying that new. Is it the correct, exact matching coil?
    Is the battery harness black jumper wire present? It's a black wire in a ''little loop''. No jumper wire, no spark... Did you ground the green wire on the cdi kit to a good ground? Re check the cdi wiring also and the battery fuse. It may have blown.
     
    #8 OLD CT, May 28, 2021
    Last edited: May 28, 2021
  10. Jeff N

    Jeff N New Member

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    Yeah i am at the point for someone fresh to look at it but I cant find anyone close to Charlotte NC.
     
  11. Jeff N

    Jeff N New Member

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    Hey Old CT, In answers to you questions: You asked about the new coil earlier and I sent you the info on the one I got. You said it looked like a match. The battery harness black jumper wire is present. The green wire is grounded at the coil. I had to drop the motor again to get that done. I dont know about the CDI wiring. Everyone on this site recommends OHTOKC and I bought his unit. Everyone here says its easy plug and play. I have a good fuse from the battery.
     
  12. OLD CT

    OLD CT Well-Known Member

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    PM sent.
     
  13. Jeff N

    Jeff N New Member

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    So I sent a desperate message yesterday morning when I was about to give up on these CT70’s. The electrics drive me nuts! Old CT reached out and offered his expert help. I met him today and he analyzed my bike. Within 5 minutes he found the fix! The new CDI ignition had a wire misplaced. I HAVE A STRONG SPARK!!!! Thanks Old CT for the fix, advice, and especially the ride on CT’s through the neighborhood!
     
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  14. OLD CT

    OLD CT Well-Known Member

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    So I just walked in from Jeff's awesome K2, The CDI conversion guy sent Jeff a kit that has the same plug as the harness. Jeff reached out to him and had to wait a couple more weeks just to have every single wire placed in the plugs wrong :( I just sorted it out and looking forward to a big order of different things to straighten out this bike from CHP to arrive. I am going to put a fresh clutch in as it's slipping bad and I tightened up the steering neck bearings for him. I am having fun working on Jeff's little blue K2.(y)

    This is what this site is all about for me, great to meet you today also Jeff, and talk soon!
     
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