I have a lawn tractor with a Briggs and Stratton 16.5hp engine. It seems over the last few years I have had to replace the battery every spring, and when I do, I have to put it on a charger after a couple of mows. The ampmeter next to the ignition does not move at all when I do get it started. A few years ago, I did jump it off of a vehicle. Which I now know I possibly ruined the regulator. I found an alternator and a regulator, but would like to know how to go about troubleshooting and where I should start. The engine is Model#313777-0163-E5. I also put a voltmeter on the battery, and got 12.5 volts when I tried to start it. It pulled down to aroud 6 volts without starting and when i turned the key off it gradually climbed back to 11 volts. Any help would be greatly appreciated.