2015 Street 750. 30,000 miles. Starter kicks in then out like a bad bendix on an car. Clearly not a battery or connection issue.
So time to open it up and have a look.

 

Heck with it open it up. Of course you really do need the Rotor assy Puller and locking tool to get it apart.
For the record The rotor assy is sold as one part you can not get the bearing that is in it. The gear bearing you can get.
Seems a 94 cent part was the problem. Woodruff key sheered off.

 

Those that own Street 750/500's are looking at being on your own. HD dropped them and easy to understand why.
Many dealers do not want to work on them . They use many tactics to push you away as some have seen.
Having some of the tools needed will be a big plus.
The So called Rotor puller Part number 51463 is a joke. It is a Bolt metric fine thread but you can get one. The locking block is a bit harder to find laying around. You will need it. The rotor is part of the starter system once it fails to lock in and or disengage it must be replaced. Some fail as low as few 1,000 miles others last 30,000 miles Plus.