This is a product that we designed, built and put to use in our Spinreel Dunebuggy Rentals Inc.
They were powered by various 4-stroke engines, Briggs 8hp. 10 hp. 12 hp. and 18 hp. Tecumseh 12 hp. It was the 12 hp. Tecumseh that we finally used because of their dependability and resistance to sand. They had very good low end torque and a top speed of about 35 mph. They were very tough. Our customers tested them on large trees trom time to time and could handle a rollover with no injuries to the customers as long as they followed our instructions. I am sure some of these little buggers are still running around the Coos Bay Sand Dunes. 
("Oregon Dunes National Recreational Area")