Deltarider:
It's not a matter of English skill, but flexibility. You know that English is a very fluid language, and especially with people like us who live within a subculture (motorcycle riders) there are terms that we use that other English speakers don't. And then we have our regional dialects too, so British riders and American riders have their own ways of saying things, and we have no power to unify what is spoken. Words change and you absolutely must be flexible. You just have to, and that's it.
"Bags" are all luggage. Even those aluminum boxes on KTM and BMW can be referred to as "bags" if we're talking about motorcycles. It's doesn't matter that they are boxes...they're bags too. Same with suitcases: hard or soft isn't the "case" (joke there). Most of us never, ever carry a suit in our luggage, but they are called "Suit" cases.
I could go on and on about the strangeness of English. British love to tease us about our usage, but the fact is, they don't speak the way their great-grandfathers did, and quite a lot of British English is FRENCH. I've heard British bikers say "Panniers" which is French.
Last point, a full-dress Harley Davidson, with fairing and 3 boxes on it, is called a "Bagger". Stay flexible cousin, or you'll have stress.