Help with 1978 Yamaha xs750 electric starter issue

Ok I posted in motorcycles and other threads and thought maybe you guys could help me. So whenever I would try to start the bike I would get a single click from the ignition unit whenever I would press the engine start button. The battery is fully charged and all electrics to the battery are now disconnected besides the positive and neg. What could this be? Solenoid, starter motor or what? Thanks guys for the help, hope to have pics of the bike up sometime soon! via /r/CafeRacers https://www.reddit.com/r/CafeRacers/comments/900ms2/help_with_1978_yamaha_xs750_electric_starter_issue/?utm_source=ifttt