[1][2] While developing the Pterodactyl Pfledge flying wing ultralight in the late 1970s, designer Jack McCornack experimented with a number of possible engines.
[2] McCornack settled on a snowmobile engine produced by the Cuyuna Development Company as having the best potential.
Lowering the compression ratio not only de-rated the engine, but also made pull-starting easier and allowed it to run on lower-octane regular auto fuel.
The resulting engine worked well, was de-rated to produce 30 hp (22 kW) at 5,500 rpm and proved reliable in service.
The modification reduced its displacement to 339 cc and output to 25 hp (19 kW) at 5500 rpm.