Topic: Why is my bike overcharging?

[Patrick]

Bike: 1969 CB750

Issue: The bike is charging at over 15 volts at the battery.

What I've done: Figuring it was the voltage regulator, I switched out the regulator. No change. Figuring it was my own ineptitude, I checked both voltage regulators by installing them on my 1975 K5 750, which charges correctly (14.3 to 14.4 volts at 4,000 rpm). With either regulator installed, the K5 still charges at 14.4 volts at 4,000 rpm.

What else I can do: ?

Why else could a bike overcharge? And why wouldn't the voltage regulator restrict it?

All testing was done with a fresh, full charge on the battery.

I am at a loss.

Patrick

[InaneCathode]

Hmmmmm, it could be your battery, if its severely sulphated the battery voltage jumps way up without 'actually' being that high.
How old is your battery?

[Patrick]

The battery was new in October. The bike hasn't been ridden much since then (maybe 500 miles) because it competes for attention with several others....

[TwoTired]

Check the voltage reading at the black and green terminals of the regulator, (Key switch on).
Immediately compare that reading to the voltage across the battery terminals.  Move BOTH measurement probes.

If the regulator gets low voltage, it "thinks" the battery needs charging, and tells the alternator to give all it's got.

Make sure the main wire harness frame ground is clean and making good contact with the frame.

Cheers,

[InaneCathode]

I'll second the dirty connections. If the regulator isnt sensing correctly it'll output incorrectly.