Engine engineering

Proof that an air-cooled engine can hit the latest emissions targets

CYLINDER HEAD

Retro looks demand air-cooling, but there is also a substantial oil-cooler, and clever design allows oil to remove much heat from the cylinder head. Single overhead camshaft operates four valves-per-cylinder.

CRANKSHAFT

270° crankshaft results in V-twinesque power delivery with uneven firing impulses. Original British twins had 360° cranks and even firing pulses. Balancer shaft is gear driven, and sits ahead of the crank.

INDUCTION

Twin throttle bodies have cable control from the twist grip, with fuel metering controlled by Bosch fuel injection and engine management. Modest 9.5:1 compression ratio means that it’ll work fine on bad fuel.

POWER UP?

The crankshaft’s substantial bearing area, and the hefty alloy crankcases suggest that the engine could comfortably deliver more power. Compression, capacity and revs could be raised on future models.

TRANSMISSION

Six-speed gearbox has evenly spaced ratios and a slick, positive action. Clutch action is eased by ‘assist’ feature; it’s light. Slipper clutch design reduces risk of wheel lock on clumsy downshifts.