Judging by the looks of it, that's one of the old Chrysler Power Bee engines. About 6.5 HP, and 134CC on the 820. Chrysler bought out West Bend's (small appliance maker) small Engine division in 1965, and sold these under the "Chrysler Marine" division. If I recall, they were used on the Chrysler Sno-Runner, Arctic Cat Screamer mini bike, Rokon TrailBreaker, and several different Go Kart Manufacturers.
West Bend also had their own line of Go Karts, but I dunno if Chrysler continued building whole Go Karts after buying them.
I would love to find an old Chrysler era Power Bee, and put it on a mini bike. Those engines really scream!
Anything Pre-1965 is West Bend, 1965-1980's is Chrysler, and 1992-present is US motor.