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  1. #1
    CB750 Member gregb6718's Avatar
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    Internal sound, then no power at all

    Hey guys, hoping you have an idea what has happened to my 1982 Super Sport. I was warming it up prior to heading in to work, standing there holding the Choke out, when I heard a sound like something spinning internally touched something stationary inside the engine and came to a stop. Not sure which side it was on, but the result was the bike died and there was no power. No Oil light. No Neutral light. No headlight. Starter wouldn't turn over. I had to throw my backpack in the truck and get to work ( where I am now) so I had no time to do more than check fuses. Main fuse at starter relay not blown. None of the five glass fuses at the handlebars were blown. I've put 1,000 miles on it since I bought it and got it roadworthy.

    Anybody have any thoughts about what may have happened in there? Thanks

  2. #2
    CB750 Guru amc49's Avatar
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    The only way I could imagine all that would be if the alternator stator or something close came loose and it should have blown the main fuse.

    I would remove alt cover anyway to slowly turn the motor in a CLOCKWISE direction several times to see if you hear anything loose hitting and to simply make sure engine is not locked up. It will allow you to view the alt rotor too for signs of contact.

    No power with no main fuse blown points at ignition switch, if replaced, the cheap crap Chinese ones can have the plastic bottom come out of place to break main connections but that makes no noise. If your ears are really sharp maybe something coming undone in plug wires or coils to possibly repeat short with each firing impulse to make a snapping noise? Check your engine grounds to make sure a bolt hasn't come off. Top rear engine mount bolt has a real big ground on it.

  3. #3
    CB750 Member gregb6718's Avatar
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    Thanks for your reply, amc49. I'll have a chance to dig into it tomorrow and try to figure it out. As far as I know, the ignition switch is 38 years old, so I guess it doesn't owe me anything.

  4. #4
    CB750 Guru amc49's Avatar
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    Get down low and check out the bottom of it, the plastic simply snaps in place and if it comes loose the terminal plate then comes loose to not connect wires. It's an instant stop if it happens, my CB550 did it.

    That doesn't explain your noise though.

  5. #5
    CB750 Member gregb6718's Avatar
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    Finally had a chance to dig into this issue today. I think it was the ignition switch, but I'm not sure. This was one of those things where you look at everything it might be, plugging and unplugging things, cleaning contacts to bright and shiny, and you don't find anything obvious, but it works when you put it all back together. I did swap the little copper contact pieces in the ignition switch. One of them looked like it was doing more work than the other, so I moved the better looking one into its position.

    If the cheap ignition switches come apart that easy, this original Japanese one was determined NOT to come apart short of dynamite and a jackhammer.
    Finally got it, though.

    I guess the noise I heard was just the death rattle of the engine as it died. The starter is giving clues that it's failing. It'll crank for 5-6 seconds and then make a noise like the gear has disengaged and that's that for that try.

    Anyway, it started and warmed up and I went for a beautiful East Tennessee fall afternoon ride. Thanks for your suggestions, amc49!

  6. #6
    CB750 Guru amc49's Avatar
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    The starter clutches are well known for rattling, they commonly loosen at the 3 bolts holding the housing together. Loctite to cure. Problems can be past that though, the 3 roller setup just sucks there. The noise you heard was one of the rollers coming loose to skid and the clutch unlocks then.

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