Foundation (1956)

Keihin was established on December 19, 1956 as Keihin Seiki Manufacturing Co., Ltd. in Kawasaki, Japan. The company’s initial goal was to manufacture precision automotive parts, with a strong emphasis on fuel delivery systems.

In 1957, Keihin successfully developed one of its first motorcycle carburetors, which was adopted by Honda motorcycles, marking the beginning of a partnership that would define the company’s history.

Growth During the Motorcycle Boom

During the 1960s and 1970s, Japan experienced rapid growth in motorcycle production. Keihin became one of Honda’s primary suppliers of carburetors and later expanded its customer base to include many international motorcycle manufacturers.

Major milestones included:

• 1963 – Developed carburetors for Honda automobiles.
• 1964 – Listed on the Tokyo Stock Exchange.
• 1969 – Opened its main carburetor manufacturing plant.
• 1974 – Produced carburetors for Honda’s CVCC engines, an important emissions technology.

Although Keihin became famous for carburetors, the company continuously expanded into advanced automotive electronics.

By the 1980s and 1990s, it had begun producing:

• Electronic Fuel Injection (EFI)
• Fuel injectors
• Engine Control Units (ECUs)
• Hybrid vehicle control systems
• Air-conditioning systems
• Power control units
• Fuel cell technologies

As emissions regulations became stricter worldwide, Keihin shifted from mechanical carburetors to electronic engine management systems.

In 2019, Honda, Hitachi, Keihin, Showa, and Nissin Kogyo announced plans to integrate their automotive component businesses. The merger was completed in 2021, creating Hitachi Astemo (now Astemo, Ltd.).

Today, Keihin continues as one of Astemo’s product brands rather than as an independent public company.

Motorcycle Components

Keihin is best known for:

• Carburetors
• Throttle bodies
• Electronic Fuel Injection (EFI)
• Fuel pumps
• Injectors
• Idle Air Control Valves
• Engine sensors

Automotive Components

Keihin also manufactures:

• Fuel injection systems
• Air conditioning systems
• Engine Control Units (ECUs)
• Hybrid power control units
• Electronic throttle systems
• Fuel cell components
• EV-related electronics

Keihin carburetors are among the most copied and imitated motorcycle parts in the world.

Some famous series include:

PE Series

• Round-slide carburetor
• Common on 2-stroke motorcycles
• Popular for racing and classic bikes

PWK Series

• Flat-slide design
• Excellent throttle response
• Used extensively in motocross and racing
• Frequently copied by aftermarket manufacturers

FCR Series

• Flat CR (Flat Constant Radius)
• High-performance racing carburetor
• Favored for superbikes and performance tuning

CVK Series

• Constant Velocity carburetor
• Smooth power delivery
• Widely used on street motorcycles

PJ Series

• Racing-oriented carburetor
• Designed for high-RPM performance

Keihin has supplied OEM components to numerous motorcycle manufacturers, including:

• Honda
• Kawasaki
• Suzuki
• KTM
• Triumph
• Harley-Davidson
• Royal Enfield

Many motorcycles leave the factory equipped with genuine Keihin carburetors or fuel injection components.

Keihin is most closely associated with Honda.

For decades:

• Honda was a major shareholder in Keihin.
• Many Honda motorcycles used Keihin carburetors as standard equipment.
• Honda automobiles also adopted Keihin fuel injection systems and electronic components.

This close relationship helped establish Keihin as one of the world’s leading OEM suppliers.

Keihin has earned a reputation for:

• High manufacturing precision
• Excellent fuel atomization
• Reliable tuning stability
• Long service life
• Strong OEM quality standards

Because of this reputation, genuine Keihin products command premium prices and are frequently counterfeited in the aftermarket.

Keihin products have been used in:

• MotoGP
• Motocross
• Supercross
• Enduro
• Superbike racing
• Drag racing
• Flat Track

The FCR and PWK carburetors, in particular, are widely respected in competitive motorsports for their throttle response and tunability.

Historically, Keihin expanded production worldwide, establishing facilities in:

• Japan
• United States
• Thailand
• Indonesia
• Vietnam
• China
• India
• Mexico
• Brazil
• United Kingdom
• Germany
• Taiwan
• Philippines

This global footprint allowed the company to support vehicle manufacturers across Asia, Europe, and the Americas.

Keihin played a major role in the evolution of engine technology, from precision carburetors in the 1950s to advanced electronic fuel injection, hybrid systems, and electric-vehicle components in the 21st century. While the company no longer operates independently, the Keihin name remains highly regarded among mechanics, tuners, racers, and motorcycle enthusiasts, particularly for its carburetors and engine management systems. Under Astemo, its engineering expertise continues to contribute to modern mobility technologies.