GSXR 750 K8. The Original Racer Replica, Reborn
Look for the origin of the modern racer replica sportbike and it’s easy to see that it all started more than 20 years ago with one machine, the 1985 Suzuki Gsxr 750. Based on a works endurance racebike and built with a combination of compact size, light weight and high output the aluminum-alloy-framed Gsxr 750 delivered all-around performance never before seen from a street-legal motorcycle. So the competition never saw it coming when the Gsxr 750 returned to the circuit, dominating production-based racing worldwide for a decade.
History repeated itself in 1996, with another revolutionary rebirth of the Gsxr 750, based on a Grand Prix racebike and setting new standards in compact design, light weight and powerful performance. Unable to compete, other brands abandoned the 750 cm3 racing grid altogether.
Introducing the 2008 Suzuki Gsxr 750 k8. With the most powerful, efficient and cleanest-running 750 cm3 four-stroke production engine Suzuki has ever produced.
Advanced 750 cm3 Engine Technology
The 749 cm3 2008 Gsxr 750 k8 engine is a textbook example of advanced, high-performance design, built with technology developed in World Championship competition. Big bore and short stroke, with a 15,000 rpm redline.
An oversquare bore and stroke of 70.0mm x 48.7 mm produces a highrevving engine with a race-proven 0.696:1 bore/stroke ratio. Each cylinder’s two 29.0 mm intake valves are set at an angle of 10.5 degrees from the cylinder centerline, with the two 23.0 mm exhaust valves set at 12.0 degrees, for a narrow included valve angle of 22.5 degrees.
The lightweight titanium valves can be accurately controlled using single valve springs, reducing mechanical loss. The valves are operated by bucket tappets measuring 26 mm on the intake side and 24 mm on the exhaust side.
Three-ring slipper pistons feature cutaway sides, and the upper compression ring and the oil control ring on each piston is electro-plated with a chrome-nitride coating applied in a vacuum chamber using a physical vapor deposition (PVD) system.
Shot-peened chrome-molybdenumsteel- alloy connecting rods carry the pistons, and the forged crankshaft is precisely balanced to smooth power delivery out of racetrack corners.
The cylinders are integrated into the aluminum-alloy upper crankcase casting and are plated with Suzuki’s own race-proven nickel-phosphorussilicon- carbide bore coating, which increases heat transfer, durability and ring seal and is known as SCEM (Suzuki Composite Electrochemical Material).
Larger ventilation holes (now 41 mm instead of 39 mm ) linking the cylinder bores (below the bottom of the piston stroke) allow air trapped underneath each descending piston to more quickly escape to adjacent cylinders, where the pistons are rising.
The race-proven back-torque-limiting clutch is designed to reduce pressure on the clutch plates during deceleration, for smoother downshifting and corner entry. Under acceleration and especially during race starts, the clutch increases pressure on the clutch plates, reducing slip.
The exhaust system includes a new, larger, triangular-cross-section silencer designed to maximize cornering clearance while also providing the increase in internal volume needed to allow the Gsxr 750 k8 to meet the latest government sound and emissions regulations despite an increase in engine output.
Each feature a fine, Iridium-alloy electrode that produces a hotter spark (contributing to more complete combustion), and delivers double the service life of a conventional spark plug electrode.
A new starter motor built using rareearth magnets is lighter and more compact than the starter motor used on previous models, weighing 860 grams (down from 1015 grams) and measuring 92.5 mm (down from 102.5 mm) long.
An efficient, trapezoidal, curved radiator looks like it came right off a works racebike and carries a compact electric cooling fan which turns on and off based on coolant temperature. The curved design increases cooling capacity to a full 31.4 kW/h without increasing overall radiator and fairing width, an important aerodynamic consideration.
A new, larger capacity generator powers the Gsxr 750 k8 ’s additional electronic systems, with no increase in weight or external size.
S-DMS Adjustable Mapping And SDTV Fuel Injection, With Digital Engine Management
The 2008 Gsxr 750 features a powerful digital engine management system, based on a 32-bit processor with 1024 kilobyte of Read-Only Memory (ROM).
The engine management system’s massive computing power not only controls the fuel injection system that delivers outstanding engine efficiency and performance, but also operates the unique Suzuki Drive Mode Selector (S-DMS) system which makes it possible for the rider to select one of three engine control maps (regulating the fuel injection and ignition systems) to match personal preference, using a threeway switch mounted on the right handlebar.
Each map was developed using experience gained building racebike maps. Switching from one map to another is instantaneous, making it possible for a rider to select one map for one part of a racetrack and another map for another part of a racetrack.
The system also allows the rider to select a different map to suit personal preference in various riding conditions on the road, for example choosing one map for highway cruising and another map for tighter roads.
At the heart of the Gsxr 750 k8 ’s fuel injection system are two new, downdraft Suzuki Dual Throttle Valve (SDTV) double-barrel throttle bodies, each throttle body barrel carrying two injectors and two butterfly valves.
New, compact fuel injectors each have 8 smaller holes instead of the 4 larger holes used previously, producing a finer spray for better fuel atomization and more complete combustion.
The volume of fuel delivered by the injectors is controlled by the engine management system, via injector ontime. The longer the injector is turned on and spraying fuel, the greater the volume of fuel delivered to the cylinder. Primary injector on-time is calculated based on engine rpm, intake pressure (vacuum) and throttle position. Secondary injector on-time is calculated based on throttle position and engine rpm.
A new Idle Speed Control (ISC) system automatically improves cold starting and stabilizes engine idle to suit conditions, by regulating the volume of fresh air fed into the throttle body idle circuits based on engine coolant temperature.
Based on throttle position and engine rpm, the engine management system controls the Gsxr 750 k8 ’s PAIR (Pulsed- AIR) system, which pulls fresh air from the airbox and injects it directly into the exhaust ports as needed, igniting unburned hydrocarbons (HC) and thus reducing carbon monoxide (CO) emissions.
The exhaust chamber mounted underneath the engine carries a catalyzer to further reduce HC, CO and Nitrogen oxide (NOx) emissions. The exhaust mid-pipe also carries an oxygen sensor used by the engine management system to fine-tune the amount of fuel injected into the cylinders, and the Gsxr 750 k8 clears tough Euro 3 and Tier 2 emissions standards.
Fully Adjustable Suspension And A Tuned Chassis
The Gsxr 750 k8 ’s frame is engineered and tuned to improve handling at racetrack speeds, even at full lean angle.
The rear subframe, which supports the rider and the tailsection, is now simpler and lighter, with a single diecast aluminum-alloy seat rail running from the main frame to the rear of the tail on each side. The design change saves 125 grams of weight.
The aluminum-alloy swingarm is constructed of die-castings and rectangular extrusions, and the rear shock mounting system uses an aluminum-alloy link that pivots on the swingarm itself, with forged aluminum-alloy link rods connected to the frame.
The Showa rear shock has externally adjustable spring pre-load, rebound damping and both high-speed and low-speed compression damping, and rear wheel travel is 130 mm.
Showa inverted cartridge forks feature 41 mm tubes and are not only externally adjustable for spring preload and rebound damping but now also have both high-speed and lowspeed compression damping adjustability. The stanchion tubes now feature durable chrome plating, and front wheel travel is 120 mm.
Adjustable footpegs are typical on a racebike, and the Gsxr 750 k8 ’s die-cast aluminum-alloy footpegs can be moved into three different positions in a 14mm horizontal and vertical range to suit rider preference.
The Gsxr 750 k8 ’s race-proven chassis geometry includes a wheelbase of 1400 mm with 23.8 degrees of rake and 97 mm of trail. Seat height is a relatively low 810 mm, and the seating position is carefully designed to work well both for racetrack and street riding, with a relatively short reach between the handlebars and the hips of the rider.
An electronically controlled steering damper produces less damping force for lighter steering at slower speeds and parking, and delivers more damping force at highway and racetrack speeds.
Radial-Mount Front Brakes And Lighter Alloy Wheels
Front and rear wheels are lighter, more rigid and stronger, thanks to a new offset-three-spoke design with curved spokes matching the direction of wheel rotation.
The front brake system uses dual radial-mount opposed-four-piston Tokico front calipers; staggered piston sizes (30 mm and 32 mm ) help equalize pad wear, and a new 17 mm (down from 19.05 mm ) radial-pump master cylinder and small-diameter, low-expansion brake lines help increase braking leverage, performance and feel at the lever.
Dual floating front brake discs measure 310 mm in outside diameter and are 5.0 mm thick, down from 5.5 mm.
Exciting New Styling
The 2008 Gsxr 750 k8 comes with an exciting, edgy, evolutionary new look, including powerful new headlights and even more effective aerodynamics.
The new fairing carries three headlights positioned side by side, a centrally mounted 55W H11 halogen projector low beam and 60W HB3 halogen multireflector high beams on each side. When high-beam is selected, all three headlights are activated, illuminating a larger area and improving cornering visibility. A position lamp above the low-beam headlight maintains the vertically stacked theme made popular by the styling of recent Gsxr models.
The SRAD ram-air intakes are positioned as close as possible to the center of the fairing nose, where air pressure is greatest. A new louver system inside the ram-air intakes replaces the mesh screens used for previous models, straightening the air flow and reducing intake resistance, which translates into higher airbox pressure and more output.
The upper fairing is slightly wider at the handlebars, reducing turbulent drag, and the lower fairing is slightly slimmer, reducing projected frontal area.
Front turn signals are integrated into the rear-view mirrors, further reducing projected frontal area, and rear turn signals are integrated into a new, slimmer tailsection.
The rear brake and taillight use LEDs (Light Emitting Diodes) as a light source. LEDs are lighter and more durable and use less electrical power than conventional light bulbs, and allow more styling freedom. The combination of a red lens and red LEDs contributes to the richness and depth of the visible light, increasing visibility as well as making a styling statement.
The fuel tank is now slightly larger, holding 17.0 liters of fuel (increased from the previous model’s 16.5 liters), and sound-deadening material underneath the tank reduces mechanical noise.
The instrument cluster includes a stepmotor-controlled analog tachometer, a digital LCD speedometer, dual LCD tripmeters, an LCD reserve tripmeter, an LCD clock, an LCD coolant temperature/fuel injection readout and an LCD gear position indicator.
More Than A Sportbike
The 2008 Suzuki Gsxr 750 k8 is more than a sportbike. It is the direct descendent of the first Gsxr, the original racer replica.