A useful tip for you on Ducar 420cc Engine Reviews: Find relevant results and information just by one click.Early versions were air-cooled two-stroke cycle, later replaced with water-cooled configurations in 1971.The engine was upgraded to a four-stroke SOHC in 1973 to meet Japanese Government emission regulations,. Replacement Engines Ducar Your best choice. The Ducar Series of fine power equipment is characterized by advanced design, compact structure, reliable performance, easy start, low fuel consumption and noise. Thus, they are the best choice for home and work applications for the environmentally conscious user.. This Predator 79cc gas engine is the ideal all-purpose replacement for 3 HP engines. The construction and engineering on this unit have been upgraded for improved durability and service life so your equipment runs longer. This tough gas engine features a durable cast iron cylinder that withstands wear and abuse, fuel shut off for safe transport.