Try testing the starter motor directly...?
Find the positive starter cable where it attaches to the starter motor and follow it back to the solenoid post first... to verify those starter cables are hooked up right. Disconnect that positive starter cable from the solenoid post.
Then find the negative battery cable where it is bolted to the motor for ground and follow it back up to the battery negative post. Disconnect that ground cable from the battery.
Remove the battery from the bike.
Connect one end of your jumper cables to a known strong battery (a car battery is fine), red on positive black on negative.
Then on the other end of your jumper cables... the red (positive) jumper cable should be connected to the positive starter cable that you took off from the solenoid, first... don't allow that cable to touch a ground...
Then clamp the black negative jumper cable to the negative ground cable that you disconnected from the battery, momentarily.
Sparks will fly if the starter is good, so cover your eyes and be careful that heavy arcing don't melt down something when you ground that jumper cable. If the motor cranks when its jumped directly, the problem is upstream... a bad battery, a bad solenoid, cables swapped by mistake, etc.