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Well, bad news... I installed the new rotor last thursday. Everything looked good, and the system measurements were perfectly within spec for the first two days. Took it out again on Sunday, and it died on the return trip. I was out of town this week, so I didn’t have a chance to dig into it...

Thanks a lot! Re-checking the rotor was next on my list. The brushes were replaced with the rotor, though I wasn't the one who physically installed them... Edit: After pulling the stator cover and re-checking, I’m getting 0.3ohm when testing from the brushes to the black/white wires at the...

No resistance reading across the black and white stator wires.

I'm seeing 0.61V and 733ohm white to ground, and 11.38V and 0ohm (/no reading) black to ground.

Thanks for the speedy reply, Sonreir. I just went and re-checked the charging system, per https://www.denniskirk.com/learn/how-to-diagnose-motorcycle My measurements are as follows: Battery (fresh off the charger): 12.89V Battery connected, key off: 12.89V Battery connected, key on: 12.89V...

Hello all, It's been about a year since I originally posted a thread regarding my charging issues with my 750 Supersport. Long story short, I thought I had fixed the issue with a new charging system, rode it for another ~2 months before finally putting the bike away in early December. The bike...

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...

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.

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.

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)

Sonrier, Let me clarify... What I mean is that I keep the tach over 3500 even at low speed (i.e. 15-30mph). Anything above that, I'm definitely cruising in the 5-6K range.

ChopperCharles, The more I read, the more it sounds like I'm always going to have this issue, even if I do get the system running "properly". I've been trying to keep the revs at 3500 and above when riding it, but that's only feasible for so long... Now, if I were to go out and trade up to a...

Okay, so I installed the rotor and new brushes. The bike seemed to be holding a charge, so I rode it 100 miles yesterday, checking the battery every 20 or so. I had 12.5 volts, consistently, at each stop (ignition off), but when I got it home, it was reading 10.5 volts and couldn't even turn the...

cxman, Yes, I'm now realizing I started at the wrong end of the system. lol This is my first CB, so I'm sort of learning as I go. Guess I won't have to worry about charging issues ever again!

Update #2... I've installed both the new regulator/rectifier and a new stator, but I'm still only seeing 11.68 volts at idle, and ~11.85 volts from 3,000-5,000rpm (when tested at the battery terminals). The only pieces left that I can think to replace are the charging rotor and brushes, neither...

Thanks Cookie, I'm definitely going to need all the advice I can get. lol. I actually just installed a brand new battery, as the old one looked like it had been around a while. I didn't know that peak charging doesn't happen until 5K RPM, though. I had been riding around trying to keep the revs...

Hello! I've been lurking around in the electrical threads for about a week now, so I thought I might as well introduce myself. I just picked up a 1980 CB750F with 4,700 miles (pic attached). It's certainly seen better days cosmetically, but it runs and rides quite well. I'm currently sorting...

Just wanted to give a quick update on the situation... I managed to get the bike running with a new positive battery cable and fresh OE main fuse. I'm seeing 12.34 volts on the battery with no load, and 11.6 volts with the bike at idle. I couldn't get a stable resistance reading across any of...

Thanks Julian, I had considered a new wiring harness. Given the limited number of components (compared to today's bikes), it shouldn't take too much time to install. Likely, less time than it would take to check each connection individually.

Hi Sonrier, The first time the main fuse blew was when I hit the start button with the jumper cables connected. When it blew the second time, all I did was connect the battery and turn the key to the 'on' position, and back to the 'off' position. Though, I'm not sure exactly when it blew, as I...