Or maybe people just need to have the title be more clear.
eg if its a CR250
have it like '1984 Honda cr250' - that way you know its a complete bike
have it like '1984 Honda cr250 wheels and forks' - that way you know its for just parts.
I think if you word the title appropriately that would make it easier.
Naturally anyone into CR250's will still probably want to look at both threads anyway even if they are not shopping for a complete bike.