Harley-Davidson has a facility in Tomahawk that produces a lot of the fibreglass parts. I believe that the open-house coincides with the Tomahawk Fall Ride, an event that raises money for MDA. There are bike parades, raffles, music, etc. throughout the weekend.
Every year a fair number of Milwaukee-area Harley employees ride to Tomahawk. Willie G.'s attendance at this, or virtually any other event, is usually a closely guarded secret. (Being a Living Legend has its downsides too, I guess..)
One problem with the Tomahawk event is that hotel/motel accomodations in the area are somewhat limited; and are completely sold out by this time. If you are planning on visiting from a distant location, you may want to make sure you have accomodations lined up before you leave home.
tomahawk is a great week end with activitys at Sara park with venders and style show, open house at both factorys just a walk throw each factory. be prepared for lots of people in a very small town. but it is a good time. lots of venders at the speed way also. havre a good time. try Wausaw wi. for a hotel it is not that far away.