Topic: 1976 CB750F Weak Charging SOLVED

[SigEpRider]

A quick test would be to run a jumper wire from the battery positive to the white wire to field and see if you get a higher output

Like what bryanj said, saves a bunch of guess work and lets you know the alternator has the muscle needed to do the job.

Oh yeah. I think I glanced over that by mistake. However, I’d like to see if the key switch is the issue first before I jump the wires.

[SigEpRider]

Nevermind. I sent it and jumped the white wire. Yes I get increased charging up to 13.5 and beyond. This was close to 3,000 rpm. I quickly shut it down after I saw the increase charging to as to not destroy the battery.

With the system wired up regularly the charging voltage goes as high as 13.3V maybe 13.5V at 3,000 RPM and above

[bryanj]

In that case the regulator is not supplying battery boltage to the white wire EITHER
1 because its no good OR
2 because it is not getting battery voltage on the black wire due to a bad connection

[SigEpRider]

I think I figured it out during a nearly 4 hour flight to Charlotte, while pouring over a wire diagram and reviewing the comments.

This was reviewing the wiring diagram to see what the black wire from the key switch powers. I was thinking that something else could be drawing power that should go to the regulator side of the combo reg/rect. I have. Then I remembered that when I jumped the white wire from the field coil to, see if I got charging increase, I noticed the headlight turned on. I didn’t think anything about it at the time, but I realized that the white wire to the regulator should only go to the field coil. Not my headlight. My headlight also doesn’t get brighter as I ref the engine up. So clearly the headlight is wired into the same white wire from the field coil and being powered by the battery. Realize….i have an aftermarket wire harness I purchased to replace the old wire harness that was chewed up. So now I’m gonna go back to the stock harness, clean and repair it, then reinstall and see if that fixes the issue. Which I think it will.

However I will be traveling for work and personal for the next three weeks. I will post an update when I’m done. Hopefully the update will include SOLVED.

Stay tuned.

[HondaMan]

With the recent number of 'wiring inquiries' I have been getting for 750s with new harnesses being installed (not just from SOHC4.net/com), I'm suspecting something has gone awry in these aftermarket harnesses? This seems to be a new phenomena, as I haven't heard of this sort of this until the last few months - all at once.