it's a TRIUMPH!!

[mousapelli]

according to the Canon guide for the SB/RL Fuh-Q Fest Sirius' motorbike was, in fact, "an early 1970s Triumph, and at least a 650" (or so the movie says, but JKR was right there, so we'll all assume she knows what she's doing).

TRIUMPH!!!! I win!

*points at Triumph of the Last Marauder and smirks victoriously*