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Thread: Weak Spark?

  1. #1
    CB750 Enthusiast MotersickleBum's Avatar
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    Weak Spark?

    OK, i now have spark on all four BUT it looks a bit weak. it archs about 1/4" . last night i tried to get it to pop with starting fluid but failed.

  2. #2
    Old Bike Nerd grepper's Avatar
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    A trick I did on my 81 CB750K I did is to put a Relay from the Coils to the battery. So that when the coils have power, power comes directly from the battery instead of through all the switches in the wiring harness. I did do a ground up restore on the bike with new coils, wires and caps, and new procom igniters. So the only thing that is original in my ignition system is the pickup and advance.
    Drive fast and take chances

  3. #3
    CB750 Enthusiast MotersickleBum's Avatar
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    Quote Originally Posted by grepper View Post
    A trick I did on my 81 CB750K I did is to put a Relay from the Coils to the battery. .

    i could just run a 12v wire from the battery to the 12v coil wire as a test, right? which is the hot lead to the coils? there's a connector with three wires if i remember correctly..

    thanks!

  4. #4
    Old Bike Nerd grepper's Avatar
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    The black wire with the white stripe is the hot lead. The blue and yellow ones tell the coils when to spark. If you connect directly to the battery you won't be able to to turn the bike off.

    Sent from my XT1254 using Tapatalk
    Drive fast and take chances

  5. #5
    CB750 Enthusiast MotersickleBum's Avatar
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    yes, i'd have to run a switch if i left it that way. thanks for the info. i'd do that test tomorrow.

  6. #6
    CB750 Enthusiast MotersickleBum's Avatar
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    ok, before i tried to rewire i thought that i'd see if i can get it to fire with all four plugs and wires and i got it to perk until it ran out of either. that's fantastic..... now i can go through the carbs and put gas to them and see if i can keep it running.

    QUESTION: what is the stock jet size on an 81 CB750? i am going to go with pods but need to make sure that the carbs are stock before i buy new jets. and on that note: i always use www.jetsrus.com . great site....

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