2019 Kawasaki Z900RS

Compared to Kawasaki’s traditional Uni-Trak rear suspension, which mounts the shock unit vertically, with Horizontal Back-link rear suspension, the shock unit is almost horizontal. Kawasaki’s original suspension arrangement locates the shock unit very close to the bike’s centre of gravity, greatly contributing to mass centralisation. And because there is no linkage or shock unit protruding beneath the swingarm, this frees up space for a larger exhaust pre-chamber (an exhaust expansion chamber situated just upstream of the silencer). With a larger pre-chamber, silencer volume can be reduced, and heavy exhaust components can be concentrated closer to the centre of the bike, further contributing to mass centralisation. The result is greatly improved handling. 

Another benefit is that the shock unit is placed far away from exhaust heat. Because it is more difficult for heat from the exhaust system to adversely affect suspension oil and gas pressure, suspension performance is more stable. Horizontal Back-link rear suspension offers numerous secondary benefits like this.

Based on feedback from racing activities, the Assist & Slipper Clutch uses two types of cams (an assist cam and a slipper cam) to either drive the clutch hub and operating plate together or apart. 

Under normal operation, the assist cam functions as a self-servo mechanism, pulling the clutch hub and operating plate together to compress the clutch plates. This allows the total clutch spring load to be reduced, resulting in a lighter clutch lever feel when operating the clutch.

When excessive engine braking occurs – as a result of quick downshifts (or an accidental downshift) – the slipper cam comes into play, forcing the clutch hub and operating plate apart. This relieves pressure on the clutch plates to reduce back-torque and help prevent the rear tyre from hopping and skidding.

Sudden over-application of the brakes, or braking on low-grip surfaces (surfaces with a low coefficient of friction) such as wet asphalt or manhole covers may cause a motorcycle’s wheel(s) to lock up and slip. ABS was developed to prevent such incidents. Kawasaki ABS systems are controlled by high precision and highly reliable programming formulated based on thorough testing of numerous riding situations. By ensuring stable braking performance, they offer rider reassurance that contributes to greater riding enjoyment. 

And to meet the special requirements of certain riders, specialised ABS systems are also available. For example, KIBS (Kawasaki Intelligent anti-lock Brake System) is a high-precision brake system designed specifically for supersport models, enabling sport riding to be enjoyed by a wider range of riders. And by linking the front and rear brakes, K-ACT (Kawasaki Advanced Coactive-braking Technology) ABS provides the confidence to enjoy touring on heavyweight models. Kawasaki is continually working on the development of other advanced ABS systems.

When accelerating on a slippery surface, it is easy for rear wheel spin (i.e. when the rear wheel turns faster than the front wheel) to occur. KTRC was designed to prevent wheel spin that could otherwise cause the loss of control of the bike. Like ABS prevents wheels from locking up when braking, this Kawasaki-original traction control system prevents the rear tyre from slipping. Knowing that the system will intervene to prevent sudden wheel spin when, for example, the pavement comes to an abrupt end when touring, is a great source of reassurance for riders. 

KTRC uses wheel speed sensors to monitor front and rear wheel speed. When it detects wheel spin, engine power is reduced to allow rear wheel grip to be regained. KTRC also enables helps the rear wheel regain traction in situations where grip is lost temporarily, like when riding over a wet manhole cover. 

KTRC uses 3-way control, governing ignition timing, fuel volume and (via the sub-throttle valves) intake air volume. This 3-way control is what enables the system to be so smooth, resulting in a very natural feeling.

It is technologically possible for traction control systems to recover from loss of grip due to wheel spin without the rider ever realising that they had slipped. However, KTRC lets riders know when road conditions are slippery by purposely delaying intervention for an instant. Firstly, communicating an accurate picture of current road conditions and what the bike is doing, and secondly, ensuring that systems provide support for riders – this is the philosophy that drives development of Kawasaki technology.