FINSBURY/SACHS WATER PUMP KM37 AND KM48 – c. 1965

The Sachs air-cooled Wankel engines were sold by Finsbury (Aust.) as water pump engines, with direct coupled water pumps.         

These engines were classed as 4-stroke motors, but still required oil to be mixed with the petrol, like a 2-stroke engine. This was a result of difficulty in cooling the rotating piston in the rotary engine, which was easy enough with water cooled engines, but became a problem with air-cooled engines. The answer was to cool the piston with the fuel before it entered the combustion chamber. These engines came in two models: KM37 & KM48.

While Finsbury discontinued their production of rotary-engine powered water pumps due to reliability, overheating and emission problems, Sachs of Germany continued supply of the engines to power a large range of equipment, including chain saws, lawnmowers, bikes, planes and outboard engines.