Ducati ST4s

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ST4s

2002 Ducati ST4s
Manufacturer	Ducati
Production	2002-2005
Predecessor	ST2/ST4
Successor	ST3/ST3s
Class	Sport touring
Engine	996 cc 90° V-twin, Fuel-Injected, 4 desmodromic valves per cylinder, liquid-cooled
Transmission	6-speed
Wheelbase
Seat height
Weight	(2002-2003), (2004-2005) (dry)
Fuel capacity	21 L (4.6 imp gal; 5.5 US gal)

The Ducati ST4s was a sport-touring motorcycle manufactured by Ducati between 2002 and 2005.

Design

The Ducati ST4S was based on the earlier ST4, which used a detuned version of the Ducati 916 engine. Compared to the ST4, the ST4S had improved suspension and a larger engine, using the liquid-cooled Desmoquattro (four desmodromic valves) 90° V-twin engine based on the Ducati 996. The Desmoquattro was largely unchanged from the 996 Superbike, and retained a valve angle of 40°, but lost 4 mm of diameter on each of the intake throttle bodies (down from 54 mm on the 996). Chassis clearances also required the use of the more compact cylinder head design that was shared with the 748 Superbike and Monster S4. In spite of the smaller intakes, the ST4s actually made slightly more power and torque than the 996 Superbike due to the mostly straight-through design of the ST's exhaust, compared to the under-seat exhaust of the Superbike.

Otherwise it was a competent trellis framed sports tourer with a protective fairing, and standard colour matched luggage (luggage was optional on other ST series models). The ST came equipped with a center-stand, an accessory power outlet, and both the ST4s and ST3s could also be equipped with ABS from 2003.

In 2004, an upgrade to the ST line brought a slightly redesigned nose fairing and dashboard, adjustable ergonomics, a trip computer, four-way (hazard) flashers, digital speedometer, a dashboard-controlled adjustable headlight, a new seat design, Euro-2 catalytic exhaust (except USA - Euro-3 was achieved in the 2006 ST3), and a simplified CAN-bus wiring setup. The refinements reduced weight by 11 kg (24 lb) due to the lighter wiring harness and simpler support structure for the nose of the bike.

The trip computer, which was fitted from 2004, could calculate the following:

• Total trip distance
• Average speed
• Average fuel economy
• Instantaneous fuel economy
• Fuel consumed (in units)
• Remaining Fuel (in units)
• Distance to empty

Clutch

In 2004 and 2005, Ducati added a wet clutch to many models, including the ST series in 2005. This reduced the force necessary to engage the clutch.

Specifications

Engine

• Layout: Transverse, liquid-cooled 90° V-twin, belt-driven DOHC, desmodromic 4V, 996 cc.
• Bore x stroke: 98.0 mm × 66.0 mm (3.86 in × 2.60 in).
• Compression ratio: 11.5:1.
• Power (Ducati changed to using an inertial dynamometer, from a brake version, to rate power and torque in 2005. However, the engine remained unchanged):
  • 2002-2004: at 8,750 rpm.
  • 2005 only: at 8,750 rpm.
• Torque:
  • 2002-2004: at 7,000 rpm.
  • 2005 only: at 7,250 rpm.
• Maximum engine speed (electronically limited): 10,000 rpm.
• Induction: Marelli electronic fuel-injection with two 50 mm throttle bodies.
• Ignition: Electronic, single centrally-positioned spark plug per cylinder.
• Starting: Electric with anti-theft immobiliser, using a chip embedded in the key.

Transmission

• Six-speed gearbox with chain final drive:
  • Gear ratios: 1st 37/15, 2nd 30/17, 3rd 27/20, 4th 24/22, 5th 23/24, 6th 24/28.
  • Primary drive ratio: 1.84:1.
  • Final drive ratio: front sprocket 15 T, rear sprocket 38 T.
• Clutch:
  • 2002-2004: Hydraulically actuated dry multiplate clutch.
  • 2005: Hydraulically actuated wet multiplate clutch.
• Top speed: 259 km/h (161 mph).

Chassis and suspension

• Wheelbase: .
• Seat height: .
• Weight (dry):
  • 2002-2003: .
  • 2004-2005: .
• Suspension:
  • Front: 43 mm Showa inverted cartridge forks, TiN-coated, adjustable for preload, compression and rebound damping.
    • Rake: 24°
  • Rear: Öhlins monoshock adjustable for preload, compression and rebound damping.
    • ST4s-specific light-weight boxed aluminum swingarm.
    • 2002 and 2003 models had a factory-installed carbon-fibre rear mudguard. Other years used an ABS-plastic part.

Wheels, brakes and tyres

• Wheels: Light-weight, cast Aluminum, Marchesini 5-spoke.
  • Front: 3.50 x 17.
  • Rear: 5.50 x 17.
• Brakes (ABS optional 2003-on):
  • Front: Twin 320 mm discs with Brembo four-pot opposed piston callipers.
  • Rear: Single 245 mm disc with Brembo twin-pot opposed piston calliper.
• Tyres:
  • Front: 120/70 ZR17 Michelin Pilot Sport tubeless.
  • Rear: 180/55 ZR17 Michelin Pilot Sport tubeless.