The diode on briggs engines allows current to flow only one way from the alternator to the battery eventually through the charging circuit,without it battery voltage goes to ground through stator underneath flywheel when switch is on.Here are some pictures of the diode on engines,remember you are looking for the wire coming from underneath the flywheel cover.
1.Third picture down on this page is a twin cylinder,spot the wire coming from underneath flywheel cover,you can make out about a one inch bump in the wire.see at http://pass.smallenginetrblshtng.com/PG6.html
2.Second picture on this page, shows wire on single cylinder by oil stick and starter.http://pass.smallenginetrblshtng.com/Pg15a.html
Note; you can cutt one out of an old engine, just cutt the wire above the diode and leave enough to splice in to your wiring.

http://www.tulsaenginewarehouse.com/drawings/allwiring.pdf

This might help.

Ok, thanks for the pics, I found the diode, and a 8 dollar relpacement one on Tulsa Engine...Not I just have to remove the flywheel and get-r-done