The CB500X’s A2-licence friendly, 8-valve liquid-cooled parallel twin-cylinder layout offers a well-proportioned balance of compact size and willing, enjoyable power output, with an energetic, high-revving character and zappy top-end.
Already strong off the bottom, the target for 2019 development was faster acceleration through a boost in low-to-mid-range power and torque in the 3-7,000rpm range; the 4% improvement comes via altered valve timing – with ‘close’ timing accelerated by 5° – and lift increased .3mm to 7.8mm.
Feeding the PGM-FI fuel injection is now a more-or-less straight shot of airflow through the airbox and throttle bodies. The battery has been re-positioned further away (44.1mm versus 13.4mm) from the rear of the airbox intake duct to allow greater airflow; the exhaust muffler now features dual exit pipes, adding a sportier sounding edge to each pulse. Peak power of 35kW arrives at 8,500rpm, with 43Nm torque delivered at 7,000rpm.
Bore and stroke is set at 67mm x 66.8mm and compression ratio remains 10.7:1; the crankshaft pins are phased at 180° and a primary couple-balancer sits behind the cylinders, close to the bike’s centre of gravity. The primary and balancer gears use scissor gears, reducing noise. The crank counterweight is specifically shaped for couple-balance and its light weight allows the engine to spin freely, with reduced inertia.
Acting as a stressed member, the engine complements the frame’s rigidity with four frame hangers on the cylinder head. Internally the cylinder head uses roller rocker arms; shim-type valve adjustment allows them to be light, for lower valve-spring load and reduced friction.
A silent (SV Chain) cam chain has the surface of its pins treated with Vanadium, reducing friction with increased protection against wear. Inlet valve diameter is 26.0mm with exhaust valve diameter of 21.5mm.
The piston shape is based upon those used in the CBR1000RR Fireblade to reduce piston ‘noise’ at high rpm. Friction is reduced by the addition of striations on the piston skirt (a finish that increases surface area, introducing gaps in which oil can flow for better lubrication). As with the CBR1000RR, an AB 1 salt bath process, used after isonite nitriding, forms a protective oxidisation membrane.
The ‘triangle’ proportion of crankshaft, main shaft and countershaft is very similar to that of Honda’s four-cylinder RR engines and much of the internal structure and engineering is taken directly from the CBR1000RR.
The crankcase uses centrifugally cast thin-walled sleeves; their internal design reduces the ‘pumping’ losses that can occur with a 180° phased firing order. Using the same internal relief structure as that of the CBR1000RR, the oil pump features improved aeration performance, with reduced friction; a deep sump reduces oil movement under hard cornering and braking. Oil capacity is 3.2L.
A six-speed gearbox mirrors that of its RR cousin and uses the same gear change arm structure and link mechanism. New for 2019 an assist/slipper clutch enables lighter upshifts and smooths out any hard downshifts.
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