In that case (assuming you know the battery is good, the battery connections are good, etc):
test for cranking voltage going into the Clutch switch. Then close the switch and see if the voltage leaves the switch.
Then go to the underhood fusebox and check the relay there. Look for power in and out while cranking (with the clutch depressed). This relay is a slave to the piggyback solenoid.
If that is good, go to the piggyback and check for trigger power (the small wire). If it's there but it wont crank, check the battery connection on the starter. If still no-go, put a jumper cable from the motor to the frame and try again.
That should have run the system pretty thoroughly.
Good luck.