1982 honda nighthawk cb750 charging issue?

http://www.partsfish.com/oemparts/a/hon/506c645ff8...

The alternator does not have a permanent magnet like most bikes.

The rotor is an electromagnet #6

It gets magnetized by the battery.

There are brushes that rub against the rotor as the rotor is spinning to magnetize it.

The brushes are difficult to see in the picture.

They are spring loaded in the engine cover.

The brushes are ordinary carbon that ware down and have to be replaced on a regular basis.

https://en.wikipedia.org/wiki/Brush_(electric)

Remove the left engine cover - there is no oil inside

Remove the brushes and check if they are worn down past the ware lines.

Replace them if they are.

As the brushes ware down, they leave carbon deposits on the rings of the rotor that they rub against.

Those rings have to be cleaned.

They are 2 copper colored rings on the face of the rotor.

Start and run the engine with the cover off the bike - might need a jumper battery to run the bike.

As the rotor is spinning, press a "scotch bright" pad against the rings.

Stop the engine and wipe the rings with a clean towel and "contact cleaner"

Repeat until the rings look brand new.

The rotors go bad and have to be replaced.

Get the specs form a service manual.

Test the resistance between the 2 rings.

The rotor is no longer available.

They can be repaired by an "electric motor" repair shop.

Now after doing simple maintenance, check if the charging system is putting out voltage.

Install the engine cover back on the engine.

Disconnect the stator wires from the wire harness.

Electricity has to be supplied to the brushes to charge the rotor.

Attach a jumper battery to the 2 white wires.

(+) to one wire & (-) to the other wire.

Set your multimeter to 100AC volts.

With the engine running, check the voltage of each possible pair of yellow wires.

1 & 2, 1 & 3, 2 & 3

At idle there should be approx 50AC volts.

When the engine is reved, the output should increase to nearly 100AC volts.

If no, the problem lies in those components - stator, rotor, brushes.

One other possibility - if the engine cover is damaged in any way (scrapes, dents, cracks) that could throw the brushes out of alignment.

If the cover is damaged, it will have to be replaced.

I charge by the hour.

You can send the money to my avatar via pay-pal LOL

Good luck.

Lessee... you want a guess about wiring, corrosion, voltage regulator-rectifiers, DMM readings, etc. from people online who can see nothing and do nothing on YOUR bike? Why doncha take the responsibility to larnya 'bout them motorcycle electrics, take off the tank, and run through the harness and everything else electrical on the bike blah blah blah yourself?

It must be the blah blah.