get a regular jumper cable and go directly from the battery positive to the larger starter terminal on the starter. if the bendix energizes and spins the engine, pull out the choke lever, have the speed lever on high, turn the ignition switch to on - not start and try the battery cable to the starter terminal. if the engine spins but won't start you got to check a few more things.
the carb has a gas solenoid that must open. there's a molex plug. check with a meter for 12 volts when you turn the key switch to on.
try a jumper cable from the battery positive to a small terminal on the starter solenoid. if the solenoid clicks then the solenoid is working. when you turn the key switch to start and you hear NO clicks, chances are the key switch is bad, or the wire going from the switch to the solenoid is open.
