Topic: 1977 CB750F Charging Issue

[lukeralsteen]

Bit of a beginner here, but I am hoping to find some answers that I have yet been unable to find on the other charging threads.

I can't seem to find the issue in my charging system. I have now replaced the battery, stator, field coil and Regulator/Rectifier. I have also replaced the main wire harness and most of the connectors and still no changes to the charging.

Currently, the voltage at the battery maxes out at 11.5V or 12.4V without the headlight regardless of the rpms. I do not have magnetism on the bolt heads of the alternator cover with ignition on or while running. The rotor has a small scratch but is not bent or anything like that. I bought this bike last year, with this issue already I assume, and am not sure if it has been in any accidents previously.

The stator and field coil readings are a bit off from what the manual says, but maybe they are still ok?
Stator readings: 0.5 ohms (no grounding)
Field Coil: 6.9ohms (no gorunding)

Other readings
Black wire at Reg/Rec : 11.67V  (ignition on)
Red wire to Reg/Rec: 12.4V
All grounds are good.

Dynamic test:
21.5VAC on yellow wires

I put 12V straight to field coil to see if that helps magnetism and saw no changes.

Any ideas what I can or should do next? I have no clue what else to try, so any advice would be much appreciated.

[scottly]

Measure the resistance from the white field wire, disconnected from the regulator, to the battery negative post. Do you still get 6.9 ohms?

[lukeralsteen]

Yeah that one is also 6.9ohms

[scottly]

I put 12V straight to field coil to see if that helps magnetism and saw no changes.

With the white field wire, disconnected from the regulator, and connected to the + battery terminal, you still have no magnetism at the alternator cover screws? (The engine doesn't need to be running, or even the key turned on for this test)

[lukeralsteen]

[/quote]
With the white field wire, disconnected from the regulator, and connected to the + battery terminal, you still have no magnetism at the alternator cover screws? (The engine doesn't need to be running, or even the key turned on for this test)
[/quote]

That is correct.

[scottly]

Do you measure 12V across the battery terminals with the white field wire connected to the + terminal?

[lukeralsteen]

I did not check that.

I did check to see if it the field coil was ground and that was all good. But I will check that reading.

Are you thinking I could be losing power elsewhere?

[scottly]

With 12V applied across the field coil leads, there should be a strong magnetic field. Maybe you have a bad battery that shows 12V, but drops when a load is applied?