Yamaha G2 Charging System Diagnosis

[Jdebruyne]

Finally got my 1987 Yamaha G2 to run and drive and have spark. I’m not too familiar with the “starter generator” charging system. I’m assuming it works like other charging systems where the “starter generator” is similar to a stator? Then sends power to the voltage regulator and then from the regulator to the battery. I put my volt meter on the battery and has 12.43 volts. Put it in neutral and get the engine to run and it drops to 11.43 volts. To me this sounds like it isn’t charging the battery. When probing a green wire on the regulator it only has 9.4 volts. I guess my question would be does anyone have the charging system specs?
Appreciate the help.

 

[HotRodCarts]

If you ground the green wire the voltage should go up if the starter generator is good and would indicate the voltage regulator is bad. If the voltage doesn't change when you ground the green wire it's either a bad starter generator or a wiring problem.

 

[Jdebruyne]

After talking with one of my older teachers who used to be a farmer he gave me an idea to try. Apparently when starter generators sit for a long time or are disconnected from the battery they can loose their magnet field. What I did I believe is called “polarizing the field” I might be wrong. Anyways what I did was disconnected the voltage regulator. Ran a wire from the battery post. Put machine in neutral and ran the engine. Touched the end of the wire that goes from the battery post to the f1 terminal of the starter generator. Only for a couple of seconds. Yes it sparks quite a bit. I had to do it a couple of times and put a mile or two on before it started charging. Even after installing a fresh out of the box starter generator you may have to do this.

 

[Diode]

Yes I remember doing this not sure of the procedure that you described I thought I remember something about the field wire which I think is the green wire