Kawasaki Z900RS
Following the successful roll-out of the new Z900 in 2017, Kawasaki are returning to the retro category using the same platform, with the Z900RS.
The newest Z is a synthesis of the traditional and the modern elements, with a traditional In-Line Four engine backed by Kawasaki’s latest rider support technology, LED lighting and digital instrumentation.
For riders searching for a bike with character and a rich history, the Z900RS offers both, with a smooth In-Line Four tuned for strong low-mid range torque, and unhurried handling care of its lightweight trellis frame.
The resultant riding is complemented by a specially designed exhaust note from the time the rider thumbs the ignition. The Z900RS’ character is reminiscent of the legendary Kawasaki bikes of yesteryear, it is happy to run at a leisurely pace, but Kawasaki also promise it is more than capable of accommodating more spirited riding should the mood arise.
2018 Z900RS Engine
Kawasaki have made some great 900cc mills and Team Green say they have tuned this incarnation to concentrate on low-mid range power delivery. This the first time that Kawasaki has conducted sound research to craft a model’s ideal exhaust note.
The liquid-cooled, A DOHC, 16-valve 948 cm3 In-line Four engine unit is based on that of the Z900, but for the Z900RS Kawasaki engineers wanted to create an engine character completely different from its Supernaked counterpart.
While the Z900 engine has a sharp, quick-revving nature that encourages high-rpm operation, the Z900RS was tuned for low-mid range, delivering strong torque that facilitates control for riders of all skill levels. Below 7000rpm, the engine pulls more strongly than the Z900.
Downdraft throttle bodies allow intake air to travel to the engine in the shortest possible distance, contributing to performance, while good over-rev characteristics mean that power does not drop off suddenly at high rpm.
Airbox design contributes to the Z900RS’ ride feel and the diameter, length, and bend of the intake funnels were also carefully selected for their contribution to the bike’s ride feel.
36mm throttle bodies are complemented by ECU-controlled subthrottles, ensuring silky smooth response and cam profiles with shorter intake and exhaust duration focus engine performance on the low-mid rpm range. Redesigned ramps on the intake cams help reduce mechanical noise. Complementing the shorter-duration cam profiles, the compression pressure was lowered to 10.8:1.
Pistons are formed using a unique casting process (similar to forging process) that sees unnecessary material removed and hollows created to achieve the ideal thickness, this enables a light weight on par with forged pistons. Die-cast cylinder offers an ideal balance of weight and rigidity.
A crankshaft with a heavier flywheel mass also contributes to the Z900RS’ strong and smooth character and a secondary balancer eliminates excess vibration, without totally eliminating it.
With a naked bike, the engine is an important styling element, and with its simple, uncluttered design the engine adds to the bike’s presence. Engine fins built into the cylinder head create the image of an aircooled engine – a nod to the Z1.
The Z900RS’ engine cover design are also reminiscent of traditional naked models. The clutch cover and many other parts of the engine’s design feature Z1 motifs and all the engine covers are die-cast aluminium pieces, contributing to the Z900RS’ high-quality design. The engine covers are finished in black paint, adding to the high-quality appearance. The covers can also be polished to a high sheen
2018 Z900RS Chassis
Complementing a light overall weight frame rigidity and chassis geometry tuning were selected to deliver light, natural handling. Like the engine, the chassis responds to rider input predictably, going where the rider wants it to without resistance. In keeping with its retro sport model character, the Z900RS’ stance is less forward-leaning than the Z900.
A new upper-triple clamp increases the steering offset by 6mm (to 34mm), which reduces trail. This tends to have the effect of quickening the steering, in the case of the Z900RS it contributes to light operation.
Wide, flat handlebar contributes to the retro sport styling while offering a wide grip to facilitate control. Relative to the Z900, the handle grips are 30mm wider, and 65mm higher and 35mm closer to the rider, offering a more upright riding position. A wide 35° steering angle facilitates low-speed manoeuvring.
Frame’s two upper rails were moved closer together to enable the slim tank design to be realised and components of the high-tensile steel trellis frame follow the ideal pipe line. The lines of the frame were made as straight as possible, and when bends were necessary their angles were made as small as possible, resulting in a design that disperses stress extremely well.
Twin-tube type rear frame’s simple design uses primarily straight lines, and helps minimise vibration transferred through the seat. Seat height is 835mm.
Rigid-mounted at five points (forward and aft of the cylinder head, behind the cylinder, at the top and bottom of the crankcases), the engine is a stressed member, greatly contributing to the light weight of the frame and chassis.
An extruded aluminium swingarm weighs only 3.9kg, contributing to low unsprung weight, which in turn contributes to the bike’s light handling. Rear suspension positions the shock unit and linkage above the swingarm. This arrangement contributes to mass centralisation, while ensuring that the suspension is located far enough from the exhaust that operation is not affected by heat.
Large-diameter inverted fork contributes to excellent ride comfort and sporty riding potential. The high-grade fork features compression and rebound damping adjustability, enabling precise settings to suit rider preference.
The Z900RS features Kawasaki’s Horizontal Back-Link rear suspension and this choice of modern suspension (also featured on Kawasaki’s supersport and Supernaked models) offers a higher level of sporty riding potential – something that Kawasaki engineers were not willing to sacrifice. Like the fork, the linked suspension delivers a balance of ride comfort and sporty performance.
At the front, 300mm brake discs are gripped by opposed four-piston radial-mount monobloc calipers. The machined monobloc calipers feature an alumite coating and are laser-etched with a Kawasaki logo, adding to the bike’s high-quality sporty looks and a radial-pump front brake master cylinder contributes to brake touch and control.
The rear brake features a single piston, pin-slide caliper gripping a 250mm disc. Sintered brake pads front and rear contribute to the control and feel. For added braking reassurance, ABS is a standard feature on the Z900RS. The ABS unit is a compact and lightweight Nissin motorcycle ABS unit.
Original cast wheels feature flat spokes designed to look like classic wire-spoked wheels. Designed using Kawasaki’s advanced analysis technology, the wheels offer a balance of light weight and stylish looks, contributing to both handling and a design suited to the retro category. Machining on the spokes further contributes to a highquality image.
2018 Z900RS Rider Aides
KTRC (Kawasaki TRaction Control) also contributes to rider reassurance, and the Z900RS is equipped with advanced Kawasaki rider support technology. KTRC features two ride modes, offering either enhanced sport riding performance or a more restrained delivery to negotiate slippery surfaces with confidence.
Race-inspired assist & slipper clutch technology offers both a much lighter feel at the lever, as well as a back-torque limiting function that helps prevent rear-wheel hop when downshifting.
2018 Z900RS Styling
With a seamless blend of Z1-inspired styling elements and modern craftsmanship – from the iconic teardrop fuel tank to the innovative oval LED taillight – the Z900RS offers timeless good looks with an exquisite attention to detail and superb fit-and-finish that results in a very high-quality appearance.
Functional style was a priority, with a simple, yet refined design pursued. In contrast to the sharp, edgy design of the Z Supernaked models, the Z900RS uses rounded elements to emulate the retro-style design of classic motorcycles. The centrepiece of the Z900RS’ design, the teardrop fuel tank is reminiscent of the Z1.
The frame was completely redesigned to accommodate the tank’s ideal position and slim shape. Only after the fuel tank position was fixed were the seat length, tandem seat and tail cowl length all balanced for the optimal retro sport model proportions.
When designing the exhaust system over 20 variations were considered before arriving at the final design, one that emphasises the presence of the In-Line Four engine. Double-walled header pipes give the exhaust a more powerful appearance, while making it more difficult for the headers to become discoloured over time. A lack of connector pipes or exhaust devices ensures clean lines. A short megaphone silencer contributes to the Z900RS’ retro sport image. The header pipes, pre-chamber and silencer are all formed from high-quality stainless steel, and are treated to a buff finish.
A blend of retro and modern designs, the large 170mm LED headlamp casts a bright, white light for great nighttime visibility. It features six chambers (four for lowbeam, two for high-beam). Position lamps in the highbeam chambers ensure the whole lamp appears lit, like a retro-style bulb headlamp. Details like a convex lens and chromed headlamp ring add to the high-quality, retro sport design.
The design of the rear cowl was inspired by the duck-bill tail cowl of the Z1. Likewise, the oval design of the LED taillight is another homage to the Z1. Unlike standard LED taillights that appear as a collection of dots, the surface-emitting LED taillight lights up as a solid surface, creating a design that is both retro and modern.
Analogue-style speedometer and tachometer dials are complemented by a multifunctional LCD screen, balancing retro-style looks with modern functionality. The LCD has an easy-to-read, negative (white letters on a black background) display. Bullet-shaped dial cases are a fitting touch for a retro sport model, with a spindle finish on the dial faces.
From the top-quality paint chosen for the fuel tank to the high-grade coating selected for the bolts, attention to the smallest detail, carefully considered wire routing, and a clean fit-and-finish contribute to the Z900RS’ appearance.
2018 Z900RS Cafe Racer Model
In addition to the standard Z900RS, a special cafe-racer style model is also available. The Z900RS Cafe features a cafe-racer-image front cowl, black, cafe-racer image drop handlebar, its own unique seat, and original colour and graphics.
Features unique to the Z900RS Cafe:
- Cafe-racer-image front cowl
- Black drop-style handlebar
- Cafe-racer-image seat (820mm)
- Brushed finish on the silencer
- Original colour and graphics
