I don't see motorcyle as a bad habit but you can have bad habit while riding one, like disobeying traffic rules from time to time, or always in the mood to past the speed limit. Cause I'm a motorcycle user too, and sometimes I can't help myself to be fast.

One of the greatest bad habit I do in everyday life is procrastinating almost everyday, always too lazy to do things in my schedule, so whenever the deadlines are already near, I have so much work to do.