KZ 650 Electrical Troubleshooting - Help!

My 77 KZ 650 B1 has been a great runner for the last 11 years that I have owned it. Except for this past year. Allow me to explain and some of you may have a solution or where to start:
- New Battery, fully charged.
- It would run for 20 miles or so then exhibit stumbling behavior almost as if it was running out of gas. It would then just cut out leaving me to coast dead stick. No electrical signs at all when turning the key.
- Trailered home and charged the battery.
- Went for another ride, and the bike exhibited the same behavior except in about 1/2 the distance, maybe 10 miles.
- Checked fuses, ok. Checked battery, still charged.
Do I have a ground issue or a bad voltage regulator or rectifier?
I could sure use some help! Thanks in advance.

Grab your meter

Ok a few tests.

meter on DC V

red meter probe on positive battery post(the post will be the metal part of the battery the cable attaches to)
black meter probe on negative battery post
Note voltage

Turn bike on
Note voltage

Raise rpm up to 4000rpm
Note voltage

shut bike off

Hi Forrest,
Just for reference, the 1977 charging system is different from all other Kz650 charging systems.
It uses a field coil without brushes. The field coil is stationary and bolted to the alternator cover with those three screws in a triangle pattern.
The flywheel is a magnetic-field inverter.
The regulator has three wires and controls the field coil in order to control the output of the alternator.
The rectifier is separate from the regulator and 5 wires, three of which are yellow or possibly white.
The stator is also stationary and is a big ring surrounding the flywheel. It is also mounted to the alternator cover.
The system performs better than the other years, but is complicated.
There are quite a few tests you can do with a voltmeter.

You will need a decent battery that is holding a charge.

After doing the voltage test F64 spelled out we can detail further tests.

Take a look in the Kawasaki Service Manual. It describes how to test the charging components, and if there's a charging system problem it should help you pinpoint it. If you find that the charging system is working fine at least you can eliminate it as a possible source of the problem. I had a problem with my 1977 KZ650-C1 and using the instructions in the manual I rather easily discovered I had a bad rectifier. I replaced it and the problem was totally solved. If you don't have a manual there is an electronic version for the 1977 KZ650 on KZRider. Ed

Thanks guys! I will give it a go in the very near future.

P.S. Loud, You should grab Lawrence and some others, get out of the city, come out by me for a ride and cookout! I have some nice roads nearby.

That sounds great. I think Lawrence was putting another Kz together.

UPDATE:  Reviving this thread in case it helps others.  It seems I have resolved the electrical issue.  It turns out that the problem was not so much a charging issue.  It was dirty connectors.  Someone on this forum recommended cleaning connectors with electrical connection spray.  I bought DexoIT that was recommended.  I noticed that my fuse box had blown a fuse or two and melted a bit.  It was a new fuse box.  Also, a couple of the negative/ground wires leading to the main fuse looked scorched.  It appears that some of my electrical connections even though looking clean & insulated had arced and shorted.  I used some fine sandpaper to scuff the connectors.   I slipped color correct shrink tube over some of the connectors/wiring that looked to have potential to make contact and short.  I sprayed the DexoIT contact cleaner on the connections.  I allowed them to air dry.  Reconnected everything hooked up the fully charged battery and voila!  I had ignition.  Lesson learned.  Sometimes it is the simple minor things that could create a major issue.  I am going to go through the entire wiring harness while I have the tank off and be sure to clean every connector & insulate every bit of wiring that looks remotely exposed.  Thanks to the ones that help the Moto Impaired!  You are very much appreciated.     

Hey Forrest! Long time!
   Congratz on getting it sorted. Electricity is just like magic, but it needs to be able to "connect the dots".
Be safe brother.

Thanks! & Good hearing from you too!