slow crank

hey guys. I an 82 KZ1100 and its cranking really slow, doesn't even come close to starting the bike. I tried jump starting it, still cranking slow. I pulled the starter and found out it was internally shorted. I replaced the starer, and its still cranking slow. I jumped the starter solenoid, the bike still cranks slow. I turned the engine by hand with a ratchet, there is no mechanical resistance in the motor either. Any ideas of what else may be causing this issue?

start with a fresh battery .. if that battery is toast then jumping it of may never work well.

Put a voltmeter on the battery and crank it. If the voltage drops below 9V, the battery is hosed.