Alternator throwing 0 volts on 1978 CB750K

[JohnnyRection]

Then call it breaking open the system, to bypass means generally to go around a thing not using it. Careful putting battery directly to field, you may get some whopping a/c if you rev the bike up. Unregulated a/c in an alt can easily hit 75 volts in many of them.

I went around the rectifier by not using it to charge the field coil and then tested the ac coming from the alternator.
Just as I didn't hope for, the newest part of the system failed. I think I will go back to the original style of rectifier and regulator.

 

[madmtnmotors]

I went around the rectifier by not using it to charge the field coil and then tested the ac coming from the alternator.

You followed the procedure in the manual for the A/C test by disconnecting the yellow alternator wires from the bike's wiring harness before starting the bike, correct?

What kind of A/C voltage readings did you observe?

 

[amc49]

Rectifier does NOT charge field coil at all. Look at a schematic...................regulator charges field. May look the same but it is NOT.

Whatever you do or choose, point type regulators are the utter pits, solid state is so much better.............

Your last post showing me at least you are pretty lost. Twelve volts into field and spin rotor and you get a/c out of stator or broken parts. Can't get more basic than that. Don't even need a rectifier or regulator to test that.

 

[JohnnyRection]

You followed the procedure in the manual for the A/C test by disconnecting the yellow alternator wires from the bike's wiring harness before starting the bike, correct?

What kind of A/C voltage readings did you observe?

Yep. 10 volts at idle.

 

[JohnnyRection]

Rectifier does NOT charge field coil at all. Look at a schematic...................regulator charges field. May look the same but it is NOT.

Whatever you do or choose, point type regulators are the utter pits, solid state is so much better.............

Your last post showing me at least you are pretty lost. Twelve volts into field and spin rotor and you get a/c out of stator or broken parts. Can't get more basic than that. Don't even need a rectifier or regulator to test that.

That's exactly what I was saying I was going to test. Whether you are calling it field coil or field the wiring to provide the 12 volts passes through the solid state rectifier/regulator unit that I have that is pretty much new. I hooked up 12 volts to that unit that magnetizes the stator while it spins, both we not hooked up to the system. Then I started the bike and tested the stator output and that works.

Is there an actually reliable source for solid state rectifiers?

 

[madmtnmotors]

What kind of A/C voltage readings did you observe?

10 volts at idle.

10 volts A/C at the yellow leads seems low. Here is a good write up by Mike Nixon:


View attachment Honda SOHC Charging System Troubleshooting.pdf