El Motor V-Twin

Liquid-cooled, DOHC, 8-valve, 90° V-Twin engine has a bore and stroke of 98 x 66 mm

and a 996 cm3 displacement. (Photo 4)

* Valve train arrangement contributes to a shorter engine height. Instead of driving the

cams with a conventional chain looped under the crankshaft and over the top of

large-diameter cam sprockets, each set of cams is turned by an idler gear located

between and below the cam gears. A link-plate chain runs between the idler gear

and an intermediate gear, which is driven off the crankshaft at half crankshaft speed.

Making the necessary speed reduction between the crankshaft and intermediate

gear allows the cam gears to be made smaller, for shorter cylinder heads and thus a

reduced overall engine height.

* Vertically staggered transmission shafts reduce front-to-rear engine length.

An extremely short crankshaft allows a narrow engine design.

* Aluminium-alloy cylinders plated with a nickel-phosphorus-silicon-carbide coating

are light, with excellent heat transfer allowing tighter, more efficient, piston-cylinder

clearance.

* Forged aluminium-alloy pistons feature short cutaway skirts, lightweight wrist pins

and L-shaped piston rings for improved sealing and efficiency at high-rpm.

* Piston temperature is controlled via oil jets at the base of each cylinder which direct

cool streams of oil onto the underside of the piston domes.

* The digital fuel injection delivers optimum fuel combustion efficiency, yielding a linear

throttle response and improved fuel efficiency, as well as contributing to low-rpm

torque and reduced emissions.

* Each of the two 45 mm throttle bodies features dual throttle valves: a primary valve

operated by the rider via the twist grip and a secondary valve controlled by the ECU

via a torque motor. The primary valve determines maximum throttle opening.

Reading the primary throttle valve position, engine rpm and gear position, the ECU

progressively opens the secondary throttle valve to maintain optimum intake velocity.

* Injectors are positioned 30° from the throttle-body centreline and direct fuel spray

down the intake ports and onto the back of the intake valves. This configuration

contributes to improved fuel atomisation and reduced emissions.

* Optimum fuel volume required by each cylinder is determined by throttle opening

and engine rpm (under heavy load conditions), and by intake air pressure and engine

rpm (under light load conditions).

2004MY

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