Motorcycle Questions? Ask a Mechanic.
Be sure to replace battery cables if damaged or remove all corrosion on battery terminal ends and have a New battery. Be sure that you have a good ground from battery to engine to frame. A good starter company is arrowhead or folks at https://ricksmotorsportelectrics.com/ should have your starter.
It would be best to remove starter and bench test it, to ensure the starter is in good operation. If Starter works good, than its most likely bad connection within the harness. Could be either bad solenoid, or even handle bar start button could be acting up. Continuity tester will help you find the issue.