Topic: '75 CB750f white generator wire?

[mysta2]

I'm in the process of buttoning up a new rebuild with a new harness. Right now it's wired just to run. I thought I had it wired to charge too, but I never grounded the generator, so it's currently not charging. I'm using a significantly more modern RR and am a little confused on the wiring.

What is the white wire for out of the generator? The diagram seems to show it connected to a fourth coil in the generator and directly to the regulator. I thought in the smaller bikes this was a "lights on" circuit and went to the main headlight switch. I don't see this connection in my diagram

I'm sure I'll just end up running with a low beam always on system, so do I just splice this white into a yellow and ground the green?


As she sits now


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[mysta2]

It looks as if the diagram shows that only the white wire coil is grounded, so it seems as if I should be changing after all.


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[Jerry Rxman Griffin aka MuthaF'er]

The white wire goes from the regultor to the field coil. The field coil (magnet) must be powered to create the current generated from the alternator coils.

[mysta2]

Oh, that's good to know and explains why I'm not charging.

So going back to the diagram it appears that the regulator controls that magnet (otherwise it would be hooked straight into a switched hot)

Can anyone explain this a little farther to help me figure out how to properly hook into my regulator/rectifier?

Can I power it from a ignition switched hot and have the magnet on all the time the bike's running with a newer R/R?


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[mysta2]

The regulator that I've got is an upgrade unit from my '94 VFR (SH701-12) which is made for this setup:



Since it's supposed to work with a permanent magnet system I'm going to go ahead and turn my generator into a permanent magnet type by powering it switched and see what happens, if my generator melts down, I'll let you know.


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[Jerry Rxman Griffin aka MuthaF'er]

The regulator has to regulate it to tell it if there is or isn't a demand. That is what the regulator is there for. That extra bullet connector sticking out in your picture has to be connected to something that is providing current to regulate the systems demands.

That r/w MIGHT work. MIGHT. But it wouldn't unless it is connected to that leftover bullet connector. You're on your own on this one.

A permanent magnet is going to provide permanent high output IMO which can/will create some serious $$ issues. Good luck finding a new wire harness, battery, rectifier, etc. Don't believe I'd attempt this! If you want to experiment then hook up the r/w to the w from the field coil behind your alternator cover.

[iron_worker]

Yes, hooking the field coil directly to 12V will overcharge your battery at higher revs. The voltage will be unregulated and you'll boil out your battery.

The idea is that system voltage is sent to a small coil (electromagnet) inside the regulator. When the voltage is high enough the electromagnet pulls a spring loaded switch open. This switch controls the electrical flow to the field coil.

High System Voltage -> Switch Open -> Cuts off Power to Field Coil -> Alternator Stops producing current -> System voltage drops -> Switch closes -> Power sent to field coil -> alternator starts producing current -> system voltage increases

Repeat many times very quickly ... and that is how the regulator works. It basically just turns the field coil on and off really fast to modulate the alternator's output.

IW

[mysta2]

So you're saying that the white wire essentially controls the regulator switching the field coil on and off with a switch inside the regulator?

So the question becomes:
How does the regulator in the diagram pictured work then? Without this wire.

And:
Is there a more compact regulator/rectifier available that I can use on a '75?


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[strynboen]

you can put a magenet in ..instead for the elektromagnet. just pull the coil in the rotor and replace it vith a magenet..then it vill work like a permanent magenet generator

[mysta2]

Found one on regulatorrectifier.com. I'll go ahead and pick that up if we decide that thus one's no good for my system.

Thanks for the info so far I'm really glad I can learn something from this experience.

I love old wire diagrams because they often explain what actually happens to an extent inside components. But in all the ones that I've seen RRs are just blank boxes full of witchcraft.


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