Snapper rider expert needed - Briggs ignition/charging

Preparing a couple of like new snapper riders for sale. Just don't use them anymore. They start and run great. Here is the problem on both. The Briggs engine has a wire coming from the magneto. Ground this wire out to metal and the engine stops. This wire also must be how the battery is charged. The magneto wire from the engine goes to a terminal screw on the side of the engine block. Also attaching to this terminal is a wire from the on/off switch and a wire going to an electrical wiring compartment. The on/off switch can be hooked to the magneto wire when the switch is on and the engine starts. Turn the switch off and the engine stops. The problem is the other wire. When it is hooked to the terminal the engines will not fire. Take it off and the engine starts right up. Looks to me like this particular wire hooks to some little plastic device in the area where the solenoid is housed. I assume this is somekind of regulator to charge the battery. Do these things short out and if it did would it ground out the magneto so the engine wouldn't start? Ever have this problem??? How is it fixed?? I just unhooked the wire and it starts and shuts off just fine, but I am sure it doesn't charge. How can the magneto make current for the ignition while not having the charging circuit ground it out??? Thank you.

Andy I can't answer your question, ignition and charging systems have always given me a fit. However, you may want to post this below on the Garden Tractor discussion board, some of those men really know small engines! Just a thought.

that little plastic thing has a zener diode in it to keep battery from back feeding into charging coil...you need it if you want engine to charge battery...it does not hook to coil in any way...should go to positive side of solenoid.

Now I sort of remember there would be two coils under the flywheel, one for the spark and one for the charging. Thanks.

unless engine is real old,the ignition coil is outside the flywheel and the charging coil is inside.

Figured it out. One wire coming out from under the flywheel cover was for grounding out the current to stop the spark. The other wires on that terminal were 1) key switch (knew that) 2) seat switch for safety (a normally closed switch until you sit down) and 3) blade "off" switch. The charging winding wires come out the other side of the engine and are in the starting wire harness. So, figured it out. Thanks.