Why not just pull the airbox cover off and jump it normally to the battery terminals. Depending on years that have the solenoid on the left frame tube, you can also attach the positive to the bat side of the solenoid and the negative to the exhaust pipe, which is an engine ground .
Putting the battery positive cable to the starter itself is wrong. All you will do is spin the starter but the rest of the electrics will still be dead or whatever voltage it is pre jumping. Not enough voltage to the ECM and system it still likely won't start, even if the starter is cranking like crazy.
Ron