Battery dying on me

Hey Gang. Could use some direction here.
Finally got my old bike back on the road. '77Kz650/810 kit, Dyna II, coil wiring upgrade, Mikuni 29's bench synched and cleaned. Battery fully charged, plugs tan.

Had the bike out the night before and put about 50 miles on it. Boy, does this old girl ever pull hard when she is on full song! About an hour into my ride I stopped and the electric start didn't have enough juice to crank over the motor. Bump started it and a few minutes later the bike started losing power like it was only running on 2 or 3. When I twisted the throttle to keep the revs up it seemed to clear itself and I was fine for the 15 minute ride home. Put the charger on and in the morning it showed 100%.

Yesterday had it out for a half hour spin the same thing happened on the way home, like it was missing. Put the charger on when I got home and it fired up again only to fade out when I took it around the block.

Had the battery tested today and it checks out. The battery will take a charge but it seems to be draining itself down.

Any ideas on what I should be looking at? Checked the wiring and fuses and everything seems okay.

Cheers -Colin

I'd check the voltage output with the bike running. I'd guess you aren't putting out enough voltage to keep the battery charged, probably a regulator/rectifier issue. MFolks has put some pretty detailed posts up on how to check the regulator and rectifier before if you can find them.

Take a look in your Kawasaki Service Manual and find the testing procedures for the rectifier and regulator. The tests are very straight forward. Start by testing the rectifier (guess how I know). If you find it or the regulator is bad you can get outstanding replacements at www.oregonmotorcycleparts.com/Products.html .

Also, you can check to make sure there is no parasitic drain when the bike is not in use. Just turn off the key, disconnect both battery cables from the battery, and test for continuity between the two battery cables. There should be none. If there is, your bike has something shorted or grounded out. Ed