[1] The basic engine was originally designed and produced by JLO-Motorenwerke of Germany and was later acquired by the AMW Cuyuna Engine Company of Beaufort, South Carolina and marketed under the Cuyuna brand name.
Later the engine was marketed by Cuyuna under the Two Stroke International (2si) brand.
[1][2][3][4] The 690 is a conventional three-cylinder engine that weighs 89 lb (40 kg) in its L70 aircraft and marine versions.
The aircraft engine features dual capacitor discharge ignition (single in the marine and industrial versions), reed valve porting, tuned exhaust system, three slide venturi-type carburetors, liquid cooling, fuel pumps, a cast iron cylinder liner, ball, needle and roller bearings throughout.
The aircraft version was offered with an optional gearbox reduction dive system and a centrifugal clutch.