Small Engines (Lawn Mowers, etc.): murray starting problems, murray riding mower, jumper cables

Question
I have a murray riding mower with a B&S engine. i bought it used so im not sure of the make, model. one day it decided to not start after years of faithful service. i bought a new battery. it wouldnt start. i took the thing almost completely apart and reassembled it, finding no major problems. it still wouldnt start. while experimenting, i took jumper cables and applied the hot cable to the positive post and the negative cable to the oil drain on the motor. it started right up. i know it probably has something to do with the safety devices or a ground problem. what did i bypass by grounding to the motor? is there a practical way for me to bypass those safety devices? any ideas? thank you in advance for your help.

Answer
You can rewire the mower to bypass the safety switches.   Do you have an electrical experience?
Do you have an OHM meter?

Have you followed the wiring harness to each safety switch and checking the connections?  Sometimes just unplugging and re-connecting the connector fixes the problem.  We also find wire insulation that has rubbed through causing a short or even broken mounting points for the switch.

Let me know.
Eric