macculloch

This MacCulloch (also thought to be offered under Homelite as well) two-stroke, twin cylinder engine was shopped around to various snowmobile manufacturers in the late 1960s to early 1970s. It used a conventional for its day Tillotson HR carburetor. What was unique about this engine design was the intake. The carb fed the fuel mix into a special chamber that effectively "stuffed" the crankcase to create more efficient combustion, and therefore greater power.
 
Pistons working off the crank at the bottom of the engine were key to making this heavy breathing engine work. Note the exposed electrics to the side of the intake. Power for this engine was thought to be in the low 40 horsepower range.

By the time the MacCulloch engine was available, all the major snowmobile brands had already locked up engine suppliers. Ski-Doo owned Rotax. Arctic Cat cut deals with Kawasaki and later Suzuki. Polaris worked closely with Fuji. And, of course, Yamaha made its own power. The best option for engine sales was to supply smaller volume brands like Homelite.