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  1. #1
    CB750 New Member Taylorecle's Avatar
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    No power to ignition switch. Or anything else.

    Hey first time posting here. I recently picked up a 1979 cb750 project bike. The guy had done a few things go the bike, new tank, tires, chain, but the electrical work was left somewhat of a mess. I'm not sure what he worked on exactly. But I was able to start it at first. Then yesterday I went to start it and nothing. Turn the key and no lights no power to the ignition switch, tested the coils and there's nothing going through them. The only power I can find is from the battery, and starter solenoid. If I connect the poles of the solenoid I hear the starter going, so something is connected right somewhere. But I cant figure out why I cant get spark, or power anywhere else. I've replaced the solenoid and the starter switch. Before and after still no dice. I'm looking now to see if it's a grounding issue, but at the moment everything seems fine. Any suggestions for troubleshooting?
    Last edited by Taylorecle; 06-09-2018 at 06:24 PM.

  2. #2
    Old Bike Nerd grepper's Avatar
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    Oct 2012
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    Could be a 100 things. There is a safety on the Clutch, could be a short someplace. Get yourself a wiring diagram and multimeter and check everything. Oe, if your afraid the harness is too cobbled up, buy a new wire harness.
    Drive fast and take chances

  3. #3
    CB750 Addict Wez_'s Avatar
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    Apr 2017
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    Do the lights on the instrument cluster illuminate when the key is switched on? If so, get a cheap multi meter from harbor freight and check for voltage using an electrical schematic. Start at the battery and move out from there. keep the black cable on the multi meter connected to the negative of the battery and move the positive probe to each component checking for voltage. You will have to keep in mind the function of each component. If checking a switch, the switch must be closed. Give you magnetic starter switch a few wacks with a small metal hammer. Sometimes they get stuck after sitting for a while or upon initial starting. This happened to me until I got everything cranking consistently. Also loose connections will yield inconsistent electrical power.

  4. #4
    CB750 Enthusiast Skelee's Avatar
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    Hamilton, Canada
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    Check ignition switch connector. Ground wire. Go from battery to solenoid. Do you hear anything?

    Sent from my SM-A520W using Tapatalk

  5. #5
    CB750 New Member Taylorecle's Avatar
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    Quote Originally Posted by Wez_ View Post
    Do the lights on the instrument cluster illuminate when the key is switched on? If so, get a cheap multi meter from harbor freight and check for voltage using an electrical schematic. Start at the battery and move out from there. keep the black cable on the multi meter connected to the negative of the battery and move the positive probe to each component checking for voltage. You will have to keep in mind the function of each component. If checking a switch, the switch must be closed. Give you magnetic starter switch a few wacks with a small metal hammer. Sometimes they get stuck after sitting for a while or upon initial starting. This happened to me until I got everything cranking consistently. Also loose connections will yield inconsistent electrical power.
    Nothing does anything when the key is on position, theres no current going through the fuse box, I feel like it's the wiring harness, but I'm hoping its something else I'm just missing. I have a multimeter I can start troubleshooting with, I'll have to go through the web of wires and see what I can find.

  6. #6
    CB750 Addict Dave's Avatar
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    Did you try turning the key back and forth several times?

    Dirt inside the switches can make them work intermittently.
    96% of the time I edit my replies so check back for updates if it isn't at least an hour old

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