"How often do you ride?"
Translation:Miten usein ratsastat?
Ratsastaa only refers to riding a horse (or a cow...or a dolphin...) For bikes, cars etc. you either use the verb "ajaa" if you are driving or something like the expression "olla kyydissä" (to be carried by) if you're not.
"Ratsastaa" has such a strong connotation with a horse that usually you don't even mention it. If you NEED to specify, it would be "ratsastaa hevosella" (it's also possible to say "ratsastaa hevosta" but that's already pretty technical lingo for expert riders)