But he's on the seat. I'm not a motorcycle person so maybe there's a way riding that motorcycle with an unconscious person works.
Well... Who's to say V actually RODE the bike with Helman on?
Could have just pushed it to town, or even walk to town after telling the bike to drive itself there (As vehicles all have the ability to auto-drive).
Or more likey, V called one of their cars and put him in that and sent their new motorcycle away (Though this does fall apart if one decides to get to this point of game without having a car - Due to the aforementioned "Your car is (Slightly dented) totalled by Delamain" scenario)
Then again, unlike with Flaming Crotch Man, this scenario doesn't necessarily require V to drive. V could have just called a Delamain cab, given that they're still on the Excelsior package (Hence V being able to be saved at the end of The Heist by calling Delamain and why V is also treated as a good friend by Delamain for his mission)