I mostly like a nice low rumble that has a constant feel to it.
The 'Vroom' most sportbikes seem to have is ok, but I don't like it when it gets too high or loud(I think it's when they get into high rpms, but not sure)
I recently found one that I despise though. I came across a motorcycle that had a "Blat, Blat" sound. It sounded like what happens to a car when it doesn't start and makes a loud noise with a puff of black smoke coming up from behind. (The thing that happened right before the end of the Race episode in Seinfeld) I had the phrase for a moment and now I can't think of it at all
