Possible alternator issue?

Hi all,

I recently bobbed a 1976 KZ400. Today I was rewiring it because when I bought it, the original harness was an absolute rat's next. In any case, I got it running for a few minutes, then I had to turn it off and move onto other tasks. When I went to restart it, something odd happened: I couldn't kick it over. The pedal felt like it was stuck. After thoroughly examining the wiring and ensuring that the pistons weren't seized (which they weren't thankfully), I found that when I do not supply power to the alternator (either by disconnecting the black ground wire from the frame, or disconnecting the green wire from the regulator) I can kick the pedal, it just won't start. Then, if I reconnect the wires so the alternator has power, I can't kick it at all. The pedal just sticks again. I'm not sure what is wrong with this. I know it isn't the battery because I even hooked the positive and negative up to my car battery. Does anyone know why this might be happening? Thanks!

Also, just for info, I am using a minimal wiring diagram courtesy of mulliganmachine.blogspot.com. I attached it below. Also, I removed the starter motor from the bike at the beginning of the project several months ago because it was shot. Thus, trying to start it via starter motor is not an option.

In that drawing, the rectifier is not shown to be grounded. It needs to be (but that is not the problem).

That is a strange symptom.

The field coil is a big electromagnet under the alternator cover on the left side of the motor. If the rotor/flywheel is loose, it is possible the field coil is causing the rotor to move and lock up against the stator or field coil. You will need to take off the cover and make sure everything is secured and not wobbling inside the cover.

Another possibility is the chain and/or starter clutch for the starter motor. If the chain is loose in there, or some starter clutch parts are loose, the magnetism from the field coil may move the parts into a place where it locks up the motor.

Yeah, I did ground the rectifier yesterday once I realized the diagram is incomplete. I'll have to take the cover off tonight once I get home and check the rotor.

Also, I removed the starter, its gear, and the chain it attaches to. I filled the hole with a regular automotive freeze plug. Thanks!

Alright, it looks like loudhvx was right. It wasn't a loose rotor, it was a loose flywheel. When I gave the alternator power, the flywheel was loose enough to shift position because of the magnetic field and stick to the rotor or the coil pack. I guess that was enough to gum up the works and freeze the kicker.

I was trying to start it again, but the fuel/air mixture is all jacked up. It'll sputter, but no start. I know this is still the electrical board, but anyone have any suggestions on how to get started?

I would check the battery first. If something shorted from the loose flywheel, maybe the battery is dead/dying. Make sure you have at least 11.5 to 12v while starting.