Ninja ZX-25R 4-Cylinder 250cc Engine Model

Publish Date2021.07.31

The Ninja ZX-25R is powered by a 250 cc, 4-cylinder engine, which many motorcycle fans had thought they would never see produced again. Kawasaki, however, turned their despair into delight: the Ninja ZX-25R prototype debuted at Tokyo Motor Show 2019. The model immediately became the center of attention and was also an instant hit when launched in the Fall of 2020.

The First 4-Cylinder 250 cc Engine Model in 30 Years

This new 4-cylinder engine, which redlines at over 17,000 rpm, achieves enjoyable high-speed sports riding, as well as smooth acceleration at low to medium speed in everyday riding. The ZX-25R is also the first 250 cc motorcycle equipped with a quick shifter that allows for clutchless gear shifting.

Speaking about the machine’s outstanding performance, Tetsuji Yamamoto, who was in charge of its development, proudly comments, “With the ZX-25R, a great riding experience is supported by cutting-edge features, such as the powerful engine which enables high-speed sports riding, and the Quick Shifter which helps the rider focus on breaking during cornering on a mountain path.”

The ZX-25R inherits the features of its predecessors, such as the Ninja ZX-10R and the ZX-6R, and embodies the belief regarding “what the ZX series should be,” shared by not only the development engineers, but also by procurement, production, and quality assurance specialists. With this new model, Kawasaki has shown its nature by leaving footprints in an unexplored area.

Bold Adoption of Cutting-edge Electronic Control - The First for the 250 cc Class

Adopted for the first time for the 250 cc class, the ZX-25R comes with an advanced, electronically-controlled system on a par with Kawasaki’s representative sports models. Kawasaki Traction Control (KTRC) offers three modes, covering a broad range of riding conditions. Kawasaki Quick Shifter (KQS) allows for clutchless up and down shifting, which reduces the physical burden on riders and supports sports riding with seamless gear changes in both acceleration and deceleration.

The handlebar area
Kawasaki Quick Shifter (KQS)

A 4-Cylinder Engine that Achieves both Powerful High-rpm Operation and Strong Low-to-Mid Speed Torque

The ZX-25R is powered by a newly-designed, water-cooled, 4-stroke, parallel 4-cylinder engine which produces 36.8 kW (50PS) of maximum power and redlines at 17,000+ rpm. Exhibiting great flexibility, this engine achieves high torque at low to medium speeds and powerful high-rpm operation.

To improve form accuracy, the cylinder head's combustion chamber is shaped and finished by machining, and to enhance intake efficiency, the shape of the intake ports is optimized. In addition, Kawasaki improved its performance by reducing friction loss at high rpms. The screaming sound at that range creates excitement for all ZX-25R riders.

newly-designed water-cooled 4-stroke parallel 4-cylinder engine

A Style that Is Hefty, Not Bulky

In terms of the width of the cowling , excluding the mirrors and handlebars, the ZX-25R is only four millimeters wider than models with two-cylinder engines, making easy the transition from a two-cylinder to a four-cylinder machine. Another feature is a riding position that makes it unnecessary to lean forward excessively in order to achieve excellent maneuverability. Its slim fuel tank enhances the sense of “oneness” with the bike when gripping with the knees.

It wasn’t easy to achieve a high-spec motorcycle that’s also easy to use in daily life

Frame Designed with a Racing Machine Concept

The ZX-25R’s chassis has been optimized as a supersport motorcycle with a 250 cc, 4-cylinder engine, based on the World Superbike Championship design concept. Coupled with its steel frame, the design of the ZX-25R makes it easier for the rider to sense the condition of both the road surface and the machine, achieving a safer sports riding experience through enhanced “oneness” with the motorcycle.

Exhaust System

The ZX-25R adopts the 4-2-1 exhaust pipe layout (4 pipes coming off the cylinder head and turning into 2 pipes before ending as a single pipe) plus a bypass pipe to keep the engine powerful even at low rpm. A 4.5-liter, high-volume chamber is connected to the single pipe section to downsize the muffler. The bike’s design is not only “cool,” but its low center of gravity and centrally-concentrated mass achieve enhanced maneuverability and agility.

Exhaust pipes
Muffler
The commercial hit of the ZX-25R is attributable to its appearance, which features a full cowling and has been praised as a “replica of the racing version.”
Senior Staff Officer
Section 1
Design Department 1
Research & Development Division
Motorcycle & Engine Company
Kawasaki Heavy Industries, Ltd.
Tetsuji Yamamoto
Senior Staff Officer
Section 3
Design Department 2
Research & Development Division
Motorcycle & Engine Company
Kawasaki Heavy Industries, Ltd.
Masato Kogirima
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