2008 Suzuki GSX-R750
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 GSX-R750.
Based on a works endurance racebike and built with a combination of compact size, light weight and high output, the aluminum-alloy-framed GSX-R750 delivered all-around
performance never before seen from a street-legal motorcycle.
So the competition never saw it coming when the GSX-R750 came to the circuit, dominating production-based
racing worldwide for a decade.
History repeated itself in 1996, with another revolutionary rebirth of the GSX-R750, based on a Grand Prix racebike and setting new standards in compact design, lightweight and powerful performance. Unable to compete, other brands abandoned the 750cc racing grid altogether.
Now, after another decade and a few extra years of total 750cc domination, the newest GSX-R750 is repeating history. Setting a new standard in racer replica engineering, delivering better handling with more power and torque in a new, more compact package designed to accelerate harder and get around a racetrack even faster than ever. Introducing the 2008 Suzuki GSX-R750. With the most powerful, efficient and cleanest-running 750cc four-stroke production engine Suzuki has ever produced.
It’s as if the talented team of engineers responsible for the GSX-R750 designed a racebike with street equipment like lights and instruments and a horn and mirrors. Which just makes it more obvious what the 2008 GSX-R750 really is.
Not just a true racer replica. The original racer replica, reborn.
Advanced 750cc Engine Technology
The 749 cm3 2008 GSX-R750 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. Double Overhead Camshafts (DOHC), and four titanium valves per cylinder operated via bucket tappets, with shim-under-bucket lash adjustment. Downdraft, dual-injector Suzuki Dual Throttle Valve (SDTV) throttle bodies and efficient Suzuki Ram Air Direct (S-RAD) induction. Liquid cooling.
A six-speed, close-ratio transmission with vertically staggered shafts, to reduce overall engine length. A back-torque-limiting clutch. And advanced digital engine management, including the revolutionary three-way, on-the-fly selectable engine mapping system known as Suzuki Drive Mode Selector (S-DMS).
An oversquare bore and stroke of 70.0mm x 48.7mm produces a high- revving engine with a race-proven 0.696:1 bore/stroke ratio. Each cylinder’s two 29.0mm intake valves are set at an angle of 10.5 degrees from the cylinder centerline, with the two 23.0mm exhaust valves set at 12.0 degrees, for a narrow included valve angle of 22.5 degrees. The narrow valve angle allows the use of a compact Twin Swirl Combustion Chamber (TSCC) designed to squeeze the most possible power out of each fuel/air charge, through the magic of combustion efficiency. With new forged aluminum-alloy pistons, the compression ratio is 12:5:1.
The lightweight titanium valves can be accurately controlled using single valve springs, reducing mechanical loss. The valves are operated by bucket tappets measuring 26mm on the intake side and 24mm 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. The chrome-nitride PVD coating is harder and smoother than conventional chrome plating, reducing friction while improving cylinder sealing, thus reducing blow-by and increasing the combustion force actually pushing the piston down. The compression ring on each piston has an L-shaped cross section, allowing combustion pressure to push the ring out against the cylinder wall and further improving cylinder sealing.
Shot-peened chrome-molybdenum-steel-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-phosphorus- silicon-carbide bore coating, which increases heat transfer, durability and ring seal and is known as SCEM (Suzuki Composite Electrochemical Material).
Larger ventilation holes (now 41mm instead of 39mm) 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 change further reduces internal pumping pressure and mechanical power losses.
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. New internal ribbing inside the aluminum-alloy clutch cover and oil pan reduce mechanical noise caused by resonance.
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 GSX-R750 to meet the latest government sound and emissions regulations despite an increase in engine output. The exhaust mid-pipe located between the head pipe collector and an under-engine exhaust chamber carries a Suzuki Exhaust Tuning (SET) servo-controlled butterfly valve to match exhaust system back-pressure to engine rpm, throttle position and gear position, maximizing torque throughout the rev range and across varying conditions.
New 10mm NGK CR9EIA-9 spark plugs 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. The individual ignition coil built into each spark plug cap is now smaller in outside diameter at 20mm (down from 22mm), reducing weight.
A new starter motor built using rare-earth 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 GSX-R750’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 GSX-R750 features a powerful digital engine management system, based on a 32-bit processor with 1024 kilobyte of Read-Only Memory (ROM). The processor is carried in a new, lighter and smaller ECM (Engine Control Module, also popularly known as an engine control black box). The new ECM weighs 340 grams (down from 380 grams) and is significantly narrower and thinner than the previous model’s ECM.
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 three- way switch mounted on the right handlebar. The three maps are designated A, B and C, and engine power delivery varies with map selection.
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 GSX-R750’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.
Each cylinder’s 48 mm primary butterfly valve is operated by the twist grip while the 50 mm secondary throttle valve is operated by the digital engine management system to maintain the ideal intake velocity (based on rpm, throttle position and gear selection) for improved cylinder charging and more efficient combustion, resulting in more linear throttle response and increased torque.
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 primary injectors operate under all conditions, and the secondary injectors add more fuel under high-rpm, high-load conditions. The primary injector for each cylinder is positioned at a steeper, 41-degree angle aimed right down the intake ports, contributing to improved throttle response across the rpm range. Each cylinder’s secondary injector is mounted at a 15-degree angle and is aimed to bounce fuel off the opened secondary throttle valve, further improving atomization and combustion efficiency. New, longer velocity stacks (also known as an intake funnels) mounted on the airbox side of each throttle body barrel help improve mid-range acceleration.
The volume of fuel delivered by the injectors is controlled by the engine management system, via injector on-time. 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 GSX-R750’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 GSX-R750 clears tough Euro 3 and Tier 2 emissions standards.
Fully Adjustable Suspension And A Tuned Chassis
The GSX-R750’s frame is engineered and tuned to improve handling at racetrack speeds, even at full lean angle. It is built by welding together five precision-cast aluminum-alloy sections, each designed to produce a specific torsional rigidity, including a hollow steering head section, two main-spar/swingarm pivot plate sections, and cross braces above and below the swingarm. The small number of component parts and welds optimizes frame assembly accuracy and performance.
The rear sub-frame, which supports the rider and the tail-section, is now simpler and lighter, with a single die-cast 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 layout reduces the lever ratio as the rear wheel moves upward, making the suspension more progressive and more responsive, increasing traction over pavement ripples while still responding smoothly over larger bumps. The system also reduces side loads, helping the rear shock absorber move in a smooth arc as it compresses.
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 pre-load and rebound damping but now also have both high-speed and low-speed compression damping adjustability. The stanchion tubes now feature durable chrome plating, and front wheel travel is 120mm.
Adjustable foot-pegs are typical on a racebike, and the GSX-R750’s die-cast aluminum-alloy foot-pegs can be moved into three different positions in a 14mm horizontal and vertical range to suit rider preference.
The brake pedal and master cylinder move with the right footpeg assembly, and the shift lever linkage can be adjusted to accommodate changes in the left footpeg position.
The GSX-R750’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. A solenoid valve operated by the engine management system moves a tapered needle away from or toward a seat in the main damping circuit, reducing or increasing oil flow for reduced or increased damping.
Radial-Mount Front Brakes & Lighter Alloy Wheels
The GSX-R750’s cast aluminum-alloy 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.
Wheel sizes are unchanged, measuring 3.50 x 17-inch front and 5.50 x 17-inch rear, but the new front wheel is 180 grams lighter and the new rear wheel is 250 grams lighter. The wheels carry new Bridgestone radial tyres designed specifically for the GSX-R750 and measuring 120/70ZR17 in front and 180/55ZR17 in the rear.
The front brake system uses dual radial-mount opposed-four-piston Tokico front calipers; staggered piston sizes (30mm and 32mm ) help equalize pad wear, and a new 17mm (down from 19.05mm ) radial-pump master cylinder and small-diameter, low-expansion brake lines help increase braking leverage, performance and feel at the lever. A stronger return spring helps keep air pressure against the front brake lever at racetrack speeds from causing brake drag. Dual floating front brake discs measure 310 mm in outside diameter and are 5.0 mm thick, down from 5.5 mm.
The size of the disc mounting bolts is slightly reduced and, combined with the slightly thinner discs, the change reduces unsprung weight and inertial mass, for better suspension action and easier turn-in on the racetrack. The single-piston Tokico rear brake caliper works with a disc that is 220 mm in diameter and 5.0 mm thick.
Exciting New Styling
The 2008 GSX-R750 comes with an exciting, edgy, evolutionary new look, including powerful new headlights and even more effective aerodynamics. The improvements in air-flow are the result of wind-tunnel development, which reduced overall drag while maintaining wind protection for the rider and while also increasing the effectiveness of the ram-air intakes. The new fairing carries three headlights positioned side by side, a centrally mounted 55W H11 halogen projector low beam and 60W HB3 halogen multi-reflector 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 GSX-R models.
The SRAD ram-air intakes are positioned as close as possible to the centre 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 tail-section.
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 litres 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 step-motor-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. An LCD engine-mode indicator displays which S-DMS performance setting has been selected by the rider. Additional LEDs are used to indicate turn signal use, neutral selection, high beam use and to warn of low-fuel. Another LED can be programmed to indicate a pre-selected engine rpm, for use as a shift light.
More Than A Sportbike
The 2008 Suzuki GSX-R750 is more than a sportbike. It is the direct descendent of the first GSX-R, the original racer replica.
Delivering Balanced Performance. On the street. On the racetrack.
Engine type: 4-stroke, inline 4-cylinder, liquid-cooled, DOHC
Bore x stroke: 70.0 mm x 48.7 mm
Displacement: 749 cm3 (749 cc)
Compression ratio: 12.5 : 1
Fuelling: Fuel injection
Oil capacity: 2.9L
Ignition: Fully transistorized
Starter system: Electric
Transmission: 6-speed constant mesh
Primary gear ratio: 1.761 (74 / 42)
Final drive ratio: 2.647 (45 / 17)
Frame: Twin spar diamond (aluminium alloy)
Rake / Trail: 23.8 degrees / 98 mm (3.9 in.)
Front suspension: Inverted telescopic, coil spring, oil damped, spring preload fully adjustable,
Rear suspension: Link type, coil spring, oil damped, spring preload fully adjustable,
compression damping 2-way fully adjustable, rebound damping fully adjustable
Front brakes: Double, Radial mount, 4-piston calipers, 310mm
Rear brakes: Single, 1-piston caliper, 220mm
Front tyre: 120/70ZR17M/C (58W), tubeless
Rear tyre: 180/55ZR17M/C (73W), tubeless
Fuel tank: 17.0 L (4.5 US gal.)
Overall length: 2,040 mm (80.3 in.)
Overall width: 715 mm (28.1 in.)
Overall height: 1,125 mm (44.3 in.)
Wheelbase: 1,400 mm (55.1 in.)
Seat height: 810 mm (31.9 in.)
Dry weight: 165 kg (364 lbs.)
Colours: Glass splash white / Pearl vigor blue (CWH) , Solid black / Metallic mat black No.2 (CRU)