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'75 CB 750 died while cranking, now no power

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bossboy302

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Was cranking over engine with fresh and fully charged battery. Was cranking great, then a "pop", then nothing-electrically dead. The "pop" sound came from the electrical area and was easy to hear since seat and side covers were off. With VOM I tested battery voltage at 12.7v. I checked main fuse-fine. Then this morning, when I turn the key on, the warning lights show a very faint glow, becoming slightly brighter, but still nothing else.
With VOM and wiring diagram I'll start tracing.
Meantime, if anyone can shed light, I'd appreciate it. My first guess is rectifier. Just a guess. Thx
 
Check negative connection to frame and make sure battery positive isn't grounding out before it gets to the starter solenoid.
 
I think the solenoid may be bad. The 12v circuit flows fairly far (not finished tracing yet), but already I have had a duplication of the original problem. Just taking connectors apart and cleaning then reassembling, I was able to get all the power back on. The warning lights glowed bright and steady. Then I hit the start button-pop-dead. Just as the first time. I was listening for it this time-definitely the solenoid. So maybe.....
 
bossboy302 said:
I think the solenoid may be bad. The 12v circuit flows fairly far (not finished tracing yet), but already I have had a duplication of the original problem. Just taking connectors apart and cleaning then reassembling, I was able to get all the power back on. The warning lights glowed bright and steady. Then I hit the start button-pop-dead. Just as the first time. I was listening for it this time-definitely the solenoid. So maybe.....
Click to expand...
Open the starter switch and give it a cleaning. I would also check the wire connection at the starter motor. The pop seems to happen when hitting that starter button so trace that circuit.
 
Will do...am systematically following the wiring, have proved out the solenoid and starter motor (by bypassing ion switch and start button)
More to follow today,,,thx.
 
A little late:
Just saw your post and you may have found the problem by now but if not...
Connect a test light between the negative and positive battery terminals at the battery. The light should be bright. Turn on the Ignition. The test light may dim but most likely it will remain bright if you are reading 12.7 volts. Instrument lights may be bright as well. Watch the test light and hit the starter button. The test light will go out. If it does, your battery is bad. You just did a load test on it and it failed.

I had the exact same problem. 12 point something volts at the battery, Ignition on, bright instrument lights. Hit the starter, "Pop" and nothing. Just like a loose batt terminal on a car. The dead giveaway was the test light directly at the battery going dead when the starter load was placed on it.

Thu
 
Last edited:
Thanks for checking in...
and you are 100% correct-battery!
In addition to doing that exact load check, I would fully charge the battery and one start attempt it would be under voltage.
New battery and good to go.
Happy New Year!
 
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