You can still do a voltage drop test even though the starter doesn't turn.
Meter set to DC V
Before the engine is hot, measure the following:
key switch on
kill switch set to run
engine not running.
Turn off the petcock
You need to disconnect the spark plug wires and ground them out or pull the red wire going to the coils (make sure the red wire isn't capable of touching metal).
I don't want the engine to start
Black probe on negative battery terminal (terminal is the metal part of the battery).
Red probe on positive battery terminal.
note voltage
hold starter button down
note voltage
Move the red probe to the positive cable stud on the starter (put the probe on the stud not the cable)
press the starter button
note voltage
Move red probe to the starter case near the starter mounting bolts--
Press starter button
The voltage should be as close to 0.0v as possible
Anything higher than 0.5v indicates too much resistance on the ground side of the starter motor.
Turn off bike
reconnect spark plugs or red coil wires
Ride bike till hot.
repeat the above tests
These tests will verify that the starter solenoid is passing full current as well as the condition of the battery.
It also checks the cables leading up to the starter motor as well as the starter's ground connection with the battery.
If all of these tests are good then the electrical to to the starter is fine.
At that point, it is either the starter's internal electrical or mechanical.
Or the engine's mechanical.