Apparently, Sirius Black's enchanted motorbike was exceptionally large:
A low rumbling sound had broken the silence around them. It grew steadily louder as they looked up and down the street for some sign of a headlight; it swelled to a roar as they both looked up at the sky – and a huge motorbike fell out of the air and landed on the road in front of them.
Philosopher's Stone - page 16 - Bloomsbury - chapter one, The Boy Who Lived
Sirius Black isn't described as a particularly large or burly guy, but I'm sure any Muggle motorbike might have been hard for Sirius to come by, based on his staunchly anti-Muggle-leaning parents. What kind of Muggle motorbike would be considered "huge", especially huge enough to hold Hagrid in Philosopher's Stone and Deathly Hallows? It would also have to be able to accommodate a sidecar, as we know from Deathly Hallows in the chapter The Seven Potters.
What brand/model was Sirius Black's Muggle motorbike?
I'm not referring to the Harry Potter movies; I'd like to know about the books, i.e. canon.