Suzuki has announced details of its first all-new four-stroke, 250cc motocross machine, which was designed in conjunction with Kawasaki Heavy Industries.

The 2004 Suzuki RM-Z250 features a compact, lightweight, and powerful Suzuki-designed four-stroke engine combined with a strong and lightweight chassis, high performance Kayaba suspension, and many other quality features to create the ultimate 250cc four-stroke motocross machine.

Engine Features

• Compact 249cc, 4-stroke, liquid-cooled, DOHC, 4-value engine designed for easy-to-ride 4-stroke power with optimum balance of crank inertia and engine brake performance (no counter-balancer system required).
• Advanced 4-valve cylinder head design with narrow 25-degree valve angle and titanium valves (31mm intake, 25mm exhaust) create a compact combustion chamber for high combustion efficiency.
• Cam profiles selected for a wide power band with strong peak power - camshafts are carburised for durability and operate steel alloy valve tappets.
• Plated aluminium alloy cylinder for increased durability, optimum engine cooling and operating temperature.
• Forged, 2-ring piston designed for maximum oil retention and minimal wear, plus tin plating for added durability.
• Keihin FCR37 carburettor with throttle position sensor and accelerator pump for increased throttle response, plus a hot-start circuit for quick engine restarts.
• Automatic decompression system for easy kick starting – simple, lightweight and designed for reliable operation, plus optional cable setup for manual operation.
• Semi-dry-sump lubrication system features separate oil chambers for the transmission and crankshaft using the transmission as the oil sump, allowing low crankshaft placement, reduced engine height and a low centre of gravity.
• Internal reed-valve between oil chambers relieves pressure from the crank chamber to reduce mechanical loss and improve high-rev performance.
• Internal oil passageways to the top end eliminate the weight and complexity of external oil lines.
• AC-CDI ignition system with two ignition maps automatically increases engine idle speed to reduce engine brake effect.
• Five-speed transmission featuring a ratchet-type shift mechanism is designed for light shifting effort and also plus compensates for differences in the shift force used by different riders.
• Thin-walled crankcase construction and magnesium valve, generator and outer clutch covers minimise overall engine weight.
• One-piece water pump and oil filter cover helps minimise engine size and weight.
• Lightweight exhaust system features a titanium and stainless steel construction, plus a repackable aluminium/stainless steel muffler.
• Aluminium skid plate with plastic side guards and aluminium engine mounting plates.

Chassis

• Lightweight twin-spar frame with D-shaped upper spars that contribute to a slim design to improved riding position and mobility.
• Slim new bodywork allows greater freedom of movement for the rider, and includes a 7.5-litre fuel tank, flat-shape seat with slip-resistant cover, long rear fender, narrow radiator shrouds and right-side cover with built-in exhaust heat shield.
• Aluminium triple clamps with rigid handlebar-mount and tapered steering stem for minimal weight.
• New Kayaba 48mm inverted, bladder-style front fork has a special valve system to optimise internal pressure and damping performance throughout the stroke – includes compact axle brackets and fork tube guards.
• Kayaba reservoir-type rear shock absorber – includes drain bolt for shock oil replacement and upper shock mount positioned for easy access to the carburettor.
• New rear linkage system (similar to RM125/250), places the suspension load on the swingarm instead of the frame to reduce frame weight, and allows smoother movement of the rear shock and linkage for improved rear wheel traction.
• Aluminium swingarm with tapered hydro-formed beams, forged axle holder, plus cast and forged linkage components – all designed for strength and minimal weight.
• Front disc brake system consists of a dual-piston caliper with 27mm pistons, master cylinder with large, 1mm piston and thin Kevlar brake line for reduced weight and progressive brake feel.
• Lightweight rear brake system includes a dual-piston caliper with 25.4mm pistons and durable forged brake pedal

The all-new Suzuki RM-Z250K4 four-stroke motocross weapon is due to arrive in Australia around September 2003, with pricing yet to be announced.

SUZUKI RM-Z250K4 - Specifications

• Engine Type: Four-stroke, single-cylinder, liquid-cooled, DOHC,  4-valve

• Displacement: 249cc

• Bore x Stroke: 77.0mm x 53.6mm

• Claimed Power: 43hp (31.6kw) @ 11,000rpm

• Claimed Torque: 28.7N-m (2.93kgf-m) @ 8,500rpm

• Compression Ratio: 12.1 : 1

• Carburetion: Keihin FCR37

• Start System: Primary kick

• Air Cleaner: Foam element

• Lubrication: Forced lubrication – semi-dry sump

• Ignition: Digital AC-DCI

• Spark Plug: NGK

• Transmission: 5-speed return

• Primary Reduction Ratio: 3.350 (67/20)

• Final ratio: 3.692 (48/13)

• Gear Ratios:
  1st: 2.142 (30/14)
  2nd: 1.785 (25/14)
  3rd: 1.444 (26/18)
  4th:1.200 (24/20)
  5th: 1.052 (20/19)

• Clutch: Wet multi-plate, manual

• Frame Type: Double main-tube, high-tensile steel (D-shaped tubes  for upper rails)

• Rake: 26.5°

• Trail: 110mm

• Steering Angle: 42° each side

• Suspension (front): 48mm inverted, cartridge type, 16-way compression and 16-way rebound damping

• Suspension (rear): Link type, adjustable preload, 16-way compression and 16-way rebound damping

• Wheel Travel (front: 300mm

• Wheel Travel (rear): 310mm

• Tyre (front): 80/100-21 51M

• Tyre (rear): 100/90-19 57M

• Brake (front): Single, semi-floating 250mm disc

• Brake (rear): Single 240mm disc

• Overall Length: 2170mm

• Overall Width: 840mm

• Overall Height: 1270mm

• Wheelbase: 1475mm

• Ground Clearance: 340mm

• Seat Height: 950mm

• Dry Weight: 92.5kg

• Fuel Capacity: 7.5 litres

• Colour: Champion Yellow