Both tires are definitely coded 317. The seller told me he thought they were the originals, and it was last licensed in 1997. So I would interpret that as the 31st week of '87 or '97 at the latest. They have lots of tread but are badly checked. I've ridden it about 4 miles now but definitely need to upgrade them before going any further. It runs amazingly well for a bike stored so long. When I took the carb apart I found that the white washer fix had already been done, which was interesting.