2019 Kawasaki Z650

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.