YES it can be done by converting to 17 inch rims. I have no idea whether TZR wheels fit that bill. Virtually any dirt bike can be converted with the right parts and enough money. The easiest method would be to have 17 inch rims and spokes laced up to your stock hubs. You could probably even keep your stock brakes then if you wanted to. If you don't want to do all that, simply order some smooth tires like Avon Venoms that are the same diameter as stock and you'll have a sportsman set-up SM.
Most members browsing this forum (including me) will not have converted a 2-stroke Yamaha and that's why I suggested you ask them over at the YAMAHA Forum if anyone has done it and how. Here's another idea as well, use the search button and search ALL forums to see if this has been covered as a topic before. This is NOT the How Do I Convert My 2-stroke Forum, its' the INTRODUCTION FORUM which you really haven't done yet before asking your first question twice.