'80 CB750F Electrical Issues

You shouldn't have to keep the tach above 3500 at all times, no. You can run off the battery for a long time and it will charge back up when you're cruising.

One thing that does help is to ditch the cheapie batteries you have to fill with acid yourself, and get a sealed battery. It helps, but the charging system is still marginal. Honestly, if I had just bought that control pod that lets me turn off the headlight, I don't think the re-wiring or going with would have been necessary. Just that and the LED bulbs I think will be enough. I mean, you have 1157 bulbs in the turn signals for front running lights, and 1156 bulbs in the rear signals. Plus two 1157 bulbs in the taillight housing. That's 8.3W for each front running light and taillight, plus 23W for each brake light and turn signal. With two taillight bulbs, that's 33 watts of power with the brake lights off. 62.6 watts with the brake lights on. Plus an intermittent extra 46 watts when the turn signals are on. And then 55 watts for the low beam. Going to LED bulbs does really help, and turning off your headlight in stop and go traffic does too. There's also now the option of LED headlight bulbs, which consume a lot less wattage and are still hella bright. They're pricey though.

Ohh, plus each bulb in your speedometer and tach housing is 3.4 watts. Two in each bucket, plus one for each idiot light. So going all LED will definitely help you a lot. It did help me back in the day.... back then though LED bulbs were a lot dimmer than they are now. You can really get some great brightness for not a lot of money these days.

I mean, I had mine working well. If I let it idle too long voltage would still drop, but it was honestly SO much better than stock. SO. MUCH. BETTER. The only times I really had trouble was when I was in stop-and-go traffic for 30-45 minutes.

Charles.

Quick update... I just charged the battery and ran through the voltage checks again, as you suggested, Sonreir. Everything checked out except for the voltage at the yellow stator wires. I was reading 10.2-11.8 V (AC) across the all three. (I did get 12V at the black and white wires)

How about when you rev it? Does the AC voltage go up?

and was the regulator hooked up while you were checking

Yes, the regulator was connected when I checked. I believe I did try rev'ing it, but I don't remember it ever getting near 20 V. Maybe 16, tops. I'll double check on that when I get home tonight.

and check rotor ohms thru the brush wires at the regulator to make sure the brushes and teh wiring are working

So, at idle I'm getting ~10 V from the stator, and 12 V at 4500 RPM. I did read 9.9 ohm at the black and white wires, though.

ok that aint right

you wont be exciting the magnet properly

better pull the cover and recheck the rotor

if the rotor is still good the check it at the wire connector for the brushes

then thru the brushes and figure out where the drop is

dont forget to test for continuity to ground there should not be any

charge the battery and have it load tested

Alright gents, the verdict is... still questionable. I ended up just throwing in the towel and taking the bike to a local shop that specializes in vintage motorcycles. They went through all the new parts, and each connection, only to find that everything was working as it should... When I went to pick it up, I spoke with the mechanic, and I explained that there was a loose pin in the rectifier connector that I had fixed before I brought it in. He seemed confident that that was what must've fixed the issue.

Now, I didn't bother to re-check the system after fixing the pin, as it seemed to have come loose after my constant fiddling with the connector. That was an oversight on my part, but it is what it is.
The bike is now working perfectly. I've ridden it another 500 miles since getting back last week, and everything seems to be good to go.

Thanks for all the help and advice, everyone! I'd also like to give a hat tip to Cafe Racer in Ypsilanti. If you're in the area, I can't recommend them enough. ;D