Model number isNNN-NN-NNNN Did use 10 w 30. Seen the regulator mounted on the side of the engine. Checked wires for looseness, all fine. Do have a voltmeter but don't know what to check. Haven't seen the alternator and don't know how to get the flywheel off.
Oil is slightly overfull. Will drain a little (probably not more than 2-3 ounces).
Problem did start very suddenly. Worked yesterday morning before changing oil, started this after changing oil. No smoke or anything, just sputters and dies. As I said the battery appears dead but starts up when jumped fine. Then sputters and dies after about a minute. That's why I was thinking alternator/electrical.