I've just had a lot of Marauder!Era feelings lately, so I wrote about Sirius buying his motorcycle.
Disclaimer: I don't own any of the Harry Potter universe characters the all belong to the fabulous JKR
The last time Sirius Black touched his parents money was the summer before his sixth year a week before he ran away
"Prongs" said Sirius on a June afternoon in the Gryffindor common room as they studied for their OWLS, or as he laid splayed out on the couch while everyone else studied
"Hm" said James absentmindedly
"I'm going to buy a motorcycle"
"A what" said James looking up from his piece of parchment, his interest now slightly peaked.
Sirius sighed "Oi Evans!"
Lily looked up from her books looking slightly confused then annoyed when she saw who called her "What do you want Black" she asked snapping at him.
"Care to explain to our dear James what a motorcycle is?" said Sirius
Lily furrowed her brow for a moment thinking about it "it's a muggle transportation device like a bike but it runs on gas" and with that Lily returned to her book.
James didn't look any less confused "Padfoot mate have you forgotten your a wizard? You can floo, you can fly, you can apperate. And you want to buy something muggles use to get around? What for" he asked
"Because" said Sirius smirking "it'll piss off my mum and dad, they'll throw a fit"
"Hm. How are you going to buy it" said James
"We both know I'm bloody loaded Prongs"
James laughed and began to write again before looking up again five minutes later
"Sirius, what's a bike?"
Sirius sighed once again "Shut up Prongs"