Get a voltmeter and measure the battery voltage WHILE you are cranking. Report back the lowest voltage you see.
It might also be helpful if you post a video of what its doing.
EDIT:
To test the solenoid. Do this:
Center stand, gear->neutral, seat off, right side panel off, look for the solenoid next to the fuse box. It looks something like this:
Key on, use a paper clip to short the two big nuts together. See if bike starts reliably.