Small Engines (Lawn Mowers, etc.): Briggs & Stratton Alternator, briggs stratton, using a multimeter

Question
I have a '71 B&S and the alternator does not seem to be charging. I have installed a new battery but charge is 12.4volts either running or stopped. Alternator has 4 wires coming out of it, 3 in one harness and 1 single(as per motor manual). how can i test the alternator using a multimeter? how can i test the rectifier?

Answer
Are you sure all 4 wires come from the alternator (stator), they aren't. 2 are ignition and 2 are charging.Find the 2 wires in the harness that are the same color. Probably brown or yellow. Test between those to wires for AC voltage. It needs to be 28+ volts AC. If you have the proper voltage the only thing you have left is the regulator. The regulator changes the charge from AC to DC volts that your battery can accept.
Some other things to test are the non-battery end of the ground cable and the back of the ignition switch. The charge usually flows from the regulator to the switch, out of the switch through a fuse or circuit breaker to the solenoid and from there back to the battery.