The 22nd annual SK-Service Japanese, British and European Motorcycle Auction and swapmeet is the oldest and longest running swap meet of its kind in the state. It’s a great event that I’ve been attending for the best of six years now. We always bring a full trailer home, and our wallets have yet to be completely empty!
From the site:

TWO BIG DAYS: Friday and Saturday, May 1st and 2nd 2009.  9 a.m -5 p.m.
Motorcycle auction held Saturday May 2nd, at noon.
Vendor setup Thursday April 30

FREE ADMISSION TO THE PUBLIC! Vendor space $40.00, auction fee $50.00/bike. No buyers fee!
Call (715) 446-2225 for consignment and vendor info.

No American Harley-Davidson’s, lawn equipment, or snowmobiles.

However: ATVs and Go-Karts are welcome! Must be 95% motorcycle or ATV related items.

Held at S-K Service Located 14 miles east of Wausau, WI or 70 miles west of Green Bay, exit 185 off Wisconsin Highway 29. WATCH FOR SIGNS! Fun for the entire family! Refreshments available on the grounds. One of the best Swap meets in the area includes ATVs and Go-Karts.

More information is available on sk-service’s website:

http://www.s-kservice.com