Sounds like the regulator has failed but the output goes through the ignition switch so it could be stopped their. You can get to the illustrated parts lists and a wiring diagram herehttp://www.partstree.com/parts/
Put Toro in the 2nd box and the 1-0141 model number in the 3rd box. You can also get the tire sizes here under Wheels and Tires.
The regulator is a bit cheaper herehttp://www.rcpw.com/Oem_Parts.htm
Select Toro-Lawnboy and enter the 101450 part number. This is a 15 amp unit and Stens has a replacement #435-084.
Have also seen where the shunt on the ammeter fails preventing the charging current from getting to the battery. You could try a temporary jumper from the regulator output terminal to the battery (+) and see if it brings the DC voltage up. Still need a battery in good condition.