the bike generates more than enough power to keep the bike running but without the battery connected the bike will not run. The alternator alone cannot keep the bike running the bike needs a battery connected at all times. This is to enable the electronics to be fed with a stable supply along with the ecu and fuel injectors etc. The bikes work on a canbus system which needs to have an uninterrupted supply. Also by removing the battery completely you may not have an earth/ground path. This does not make it a PIA but is simply how modern motorcycles with all of their electronics are made.