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  1. #1
    CB750 Member diggidan's Avatar
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    Ignition coil blown up

    Hi!

    My ignition coil made a poff noice and started to smoke and melt about 30sec after startup.

    Background info:

    I have run my bike without the regulator.
    I know, stupid af. I had a rush get it to the vehicle inspection so I left it out.
    The bike ran great so I forgot about it. Also stupid, I know...

    Anyhow, I was driving along on a longer trip and the bike suddenly died. I realized later on that the battery was swollen and I figured I had over charged it without the regulator.
    So I changed the battery and hooked up the regulator.
    I found the classic, hand drawn, simplified scheme for cb750 and hooked it up according to that.

    I fired up the bike, went fine. Although the battery just had 12v even when the bike was fired up.
    Anyway. The engine felt a bit tired and "blob-blob-blob":y.
    About 30sec later I heard a POF! and smoke squirted out from one of the coils. It melted down on the engine and I quickly stopped the engine.

    I think it's very weird that it went crap when I finally hooked up the regulator...
    It should have happened before I did that I think so I dont get it...
    I have ordered a new pair of coils and is going to swap the old ones out.
    But I'm scared to hook them up in case something else is wrong...

    But how can this happen AFTER I hooked up the regulator?
    And is something else wrong with the connections you think?

    Attaching a scetch of how I have connected everything.

    Thanks!

  2. #2
    CB750 Member diggidan's Avatar
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    Nobody knows what the problem might be?

  3. #3
    CB750 Guru amc49's Avatar
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    You shorted BOTH coils out, one just didn't do the last massive end of life short until after you fixed bike. You had already melted insulation to cross wires and just needed a little push to go the last bit.

  4. #4
    CB750 Member diggidan's Avatar
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    Quote Originally Posted by amc49 View Post
    You shorted BOTH coils out, one just didn't do the last massive end of life short until after you fixed bike. You had already melted insulation to cross wires and just needed a little push to go the last bit.
    Aaah, as I suspected...
    Weird that it got me this far.

    So you dont see any problem with my current diagram?

    Thanks so much!

  5. #5
    CB750 Member KRBJ's Avatar
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    Quote Originally Posted by diggidan View Post
    Nobody knows what the problem might be?
    All the electrics on these bikes come with smoke from the Honda plant once you let it out you can not put it back in so you did the right thing buying new ones. Now about about your bike it helps a lot if we know what bike you have. They are not all the same. You need the correct wiring diagram for your bike I can show you where to down load it and step you through how to wire it when I know what year and model it is. I would not hook the battery. up until you know it is wired correctly. Don't be a parts changer it cost to much. Get back soon. Just here to help

  6. #6
    CB750 Member diggidan's Avatar
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    Quote Originally Posted by KRBJ View Post
    All the electrics on these bikes come with smoke from the Honda plant once you let it out you can not put it back in so you did the right thing buying new ones. Now about about your bike it helps a lot if we know what bike you have. They are not all the same. You need the correct wiring diagram for your bike I can show you where to down load it and step you through how to wire it when I know what year and model it is. I would not hook the battery. up until you know it is wired correctly. Don't be a parts changer it cost to much. Get back soon. Just here to help
    Thanks for the concern!

    I got it working by replacing the coils and hook up the electrics as my wiring diagram show.
    The only thing I had to change was the set screw for the regulator. It charged about 15V when revving so I took it down a bit.
    Rode it a good distance over a weekend and it worked like a charm!

    Although, I got AAA the last bit home due to one of the bolts holding the brake caliper vibrated out and cleaned my wheel of some spokes.

    But no electrical problem! Hehe.

    Thanks for the help!

  7. #7
    CB750 Member KRBJ's Avatar
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    Quote Originally Posted by diggidan View Post
    Thanks for the concern!

    I got it working by replacing the coils and hook up the electrics as my wiring diagram show.
    The only thing I had to change was the set screw for the regulator. It charged about 15V when revving so I took it down a bit.
    Rode it a good distance over a weekend and it worked like a charm!

    Although, I got AAA the last bit home due to one of the bolts holding the brake caliper vibrated out and cleaned my wheel of some spokes.

    But no electrical problem! Hehe.

    Thanks for the help!
    WOW I'm sure that is a ride you will not forget. For brakes it is a good idea to use a torque wrench and locktite. Red for brakes.

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