A question that is often asked, “Is there a motorcycle engine in my jet ski?”
The answer…..
In the 1950s and 60s, Japanese motorcycle companies began to sell more bikes in the US, most of which were small, barely more than scooter models.
In the push to make something more viable in the US market, better motors with multi valves, overhead cams and water cooling engines were designed.
Kawasaki developed their motorcycle engine into 1100 (ZX-11) and 1400cc versions, the basis for the STX12 and STX15 jet ski models.
Yamaha came up with a revolutionary 5 valve head design with the idea if 2 smaller valves are better than 1 big valve, then 3 intake valves would be better than 2.
When Yamaha and Kawasaki decided to use 4 stroke water cooled engines in their skis, the obvious choice was to base it off their successful motorcycle designs. The heads and cylinders (including the 5 valve Yamaha head design) were used in a very similar form – but the bottom ends were very different from the motorcycle counterpart, as they didn’t have a transmission (at least not shiftable gears), and the bottom end was reinforced to survive better in the lower revving but higher stress environment of a marine engine.
So the answer to “Does my jet ski have a motorcycle engine?” is yes and no. A portion of the Yamaha and Kawasaki motor is the same as the Yamaha and Kawasaki motorcycle motors and a portion is designed specifically for jet skis.
Most other jet ski manufacturers designed and built most of their motors specifically for their jet skis.
