I would go with spark plugs of all flavors, air and oil filters, wheel and axle bearings, CV boots, U-joints (Polaris), Multiple oils of all flavors. This is what I've found in my shop to be common items. I thought when i started out that when I found the common items that I'd start stocking them but it seems that when it comes to parts, I work on too many brands to be able to stock the correct items. The majority of what I work on are Hondas just because they are so darn popular in my area. Yamahas are second with lots of them out there too and Polaris 3rd because they are unreliable (my opinion only). I'm in northern Ohio. It would be a good idea to test the waters for awhile and see what needs you have. Good luck!