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CB750c 1981 weak charge issue

MIkeZad

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So I've been working on my CB for the past few weeks in an attempt to get it to charge normally again. I've had it for 2 years, and for about 1.5 of those years, I had no issues. Now I'm stuck.

Main issue - AGM Battery at 12.6vDC when off. At idle Voltage sits at around 12.0vDC. Revved up to 5k, voltage barely cracks 13v.

Things I've done and tested
- Stator all three wires ohm fine with none to ground. Replaced with a spare that also tested good. No change
- Regulator/Rectifier changed with a Ricks at the same time as the rotor. Rotor changed twice. No change (Diodes still good)
- Main battery ground checked and cleaned multiple times
- Grounds near coils and inside headlight checked and cleaned multiple times
- Wiring harness changed as I had a fair amount of cracked plastic and poor condition wires.
- Voltage drop at the black wire going TO the stator 0.28vDC (Too much??, seems alright.)
EDIT - since I forgot
- I had my battery load tested twice and all good. I also tested with 2 brand new AGM batteries with good voltage and same exact issue.

With all lights disconnected, battery voltage reads 13.5 vDC at 3k RPM.
With lights connected, battery voltage reads 12.5 vDC Max at 3k RPM.

So clearly with no loads from lights, I can get a decent charge but that's not really good enough.
Am I missing something?
 
Last edited:
First, I'm not receiving any compensation. Talk to Tony at Oregonmotorcycleparts.com. He will fix you right up. I've done 2- 750's. The 1st was a '78 SOHC. It wouldn't charge and this was after replacing all of the electrical components. His solid state regulator/recifier assy. replaced the OEM rectifier and regulator. After installing, I had a constant voltage @ 14v. The lights were bright with no fading based on the idle. Plus he offers a LIFETIME WARRANTY. You will not get that from any electrical parts supplier
 
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