Kawasaki FX Vs. FS Engines: What's The Difference?

In addition to Kawasaki side-by-sides and motorcycles, the company makes engines for lawn mowers and other industrial and agricultural applications. Kawasaki offers its engines in a variety of series, of which the FX and FS Series engines provide the greatest variety over a wide range of power ratings. While Kawasaki's most successful motorcycles enjoy brand recognition, other products, such as zero-turn mowers, have Kawasaki engines, sometimes without displaying the Kawasaki brand at all.

Kawasaki's FX and FS Series engines are all air-cooled four-cycle V-twin designs. Power ratings range from the 38.5-horsepower 999cc (61-cubic-inch) FX1000V EFI down to the 603cc (36.8-cubic-inch) FS481V with 14.5 horsepower.

Kawasaki calls its mid-duty FS Series "a force in the field." Applications include wide-area walk-behind, stand-on, and zero-turn mowers in addition to lawn and garden tractors.

FX Series Kawasaki engines are heavy-duty, designed for commercial-grade mowers. Kawasaki lists the FX Series with similar applications as its FS Series, except for the omission of lawn and garden tractor usage.

Kawasaki's FX Series V-twin engine offerings are spread over a range of 16 models with the highest output rated at 38.5 horsepower. For comparison, the FS Series Kawasaki engines come in six models, the most powerful being the FS730V with 24 horsepower.

Given the limited number of FS Series models, it's understandable that Kawasaki offers FX Series engines with similar specs. If you need a Kawasaki engine with more than 24 horsepower for your lawn mower, you'll be forced to look beyond the FS Series. However, for engines below that rating, down to 14 or 15 horsepower, there are six models from each series that'll fit your needs.

The Kawasaki FX730V EFI produces 25.5 horsepower, but the non-EFI version of the FX730V with 23.5 horsepower compares more closely with the 24-hp FS730V. Both 730V engines feature 726cc (44.3-cubic-inch) displacements derived from the same 78mm (3.1-inch) diameter cylinders and 76mm (3.0-inch) stroke.

At the other end of the FS and FX power-comparison spectrum sits the FS481V with 14.5 horsepower and the 15.5-hp FX481V. These engines use 73mm (2.9-inch) diameter cylinders and 72mm (2.8-inch) crankshaft stroke to displace 603cc (36.8-cubic-inches). Whereas the FS481V uses dual-element air filtration, the FX481V has a multi-stage canister air filter.

The four comparable models in between share similar specs for cylinder diameter, stroke, displacement, and horsepower. However, the horsepower advantage varies to one or the other depending on the actual models being compared.