Riddenclimb: Other than the starter engage mechanism which slams a gear turned by the starter into mesh with a gear in the engine, the starter is a simple DC electric motor of a high torque design... that means it draws a good bit of power. If you have an Amp meter, test the draw. If it draws nothing, chances are you have on open ckt inside the starter motor. If it pegs the meter, you have a short ckt inside the starer motor or it is locked up and can't turn.
You've done basic testing. When you connect it directly to the batt without the starter relay in the ckt... you determined it is indeed the motor.
If you can bump start the engine, that means the starter isn't locked up to the engine...
Next, remove the starter and test it again, hot wired to a fully charge high current capable battery.
If it does not turn, the bearings in the starter are probably bad and allow the armature to "drag" hard enough to prevent it from turning. You can test this by simply tryint to turn it by hand.
If it's locked up, the suggestion of taking it to a starter/motor repair facility is EXCELLENT. These Japanese starters are very common and in many cases the motor components are not motorcycle specific. Often they are very common Nipendenzo branded inside. I have a John Deere lawn tractor. It has a Kawasaki motor with a Nipendenzo starter... the things are ubiquitious any more.
If you go to a Zuke dealer for a starter.... YOU ARE LIKELY TO BE RAPED.
If the armature in the starter is not burned or shorted and if the primary field windings are intact, chances are it can be repaired at very little cost... certainly much less than the cost of buying a new starter from Zuke.
If however, the armature is grounded internally, has burned windings, or the field windings are shot... get out your steel teeth, because it's BITE THE BULLET TIME....
JR