Thanks much bertsmobile. Incredibly helpful and just ordered it. So I'd be basically bypassing the mower's regulator.
So I can connect the new motor's red wire to the red going to the rectifier, but am not seeing any red/yellow wire on either the mower or diagram. Did you mean connect the motor's orange wire to both red and yellow on the mower?
The two other wires (black-or brown/white and black-or brown/yellow) both went directly to the stator. Would those then get spiced to the red on the new motor?
yes you are bypassing the rectifier fitted to the mower and using the one fitted to the engine.
So the DC ( red ) wire from the engine's rectifier goes to the red wire attached to the old rectifier on the mower.
The striped wires at the engine plug go nowhere and get connected to nothing as they are the old AC wires that went from the Kawasaki stator to the rectifier which you are bypassing.
Now I threw you a red herring or rather a red & yellow herring.
The orange wire on the new engine plug should go to the Yellow & black wire coming out of the old rectifier.
So you will unplug the 6 pin plug that the rectifier connects to and the red & orange wires into there.
The other 4 terminals shall remain empty.
As I read the diagram that means the battery light will always be on or will never come on depending upon how it was wired into the rectifier.
On a completely different tack, if you get back onto who ever sold you the engine and ask them if you could swap your current alternator & rectifier for a 10Amp stator that has 2 yellow wires in place of your single yellow wire then you could simply plug the yellow wires into the striped wires and use the original rectifier.
Now that I have thought about it you may have been sold the wrong engine as the alternator fitted might not be powerful enough to charge the battery and power the clutch at the same time.