Honda NC850 In The Works?

[Hugh Janus]

Patent drawings show Honda looking at a larger replacement for its NC750 model. (Japanese Patent Office/)

Take a quick look at Honda’s latest patent application—recently published via the Japanese patent office—and you’d be forgiven for thinking it shows the existing NC750S or even the original NC700 model. But look closer and it actually reveals a completely new engine that might well form the basis of the firm’s next-generation NC range.

Honda is widely expected to reveal a revamped replacement for the NC750 models later this year. Believable rumors from Japan suggest the firm will increase its capacity once again—the original NC700 was 690cc, the current NC750 is 745cc, and the next model is likely to be in the region of 800–850cc to retain performance while reducing emissions. However, if this patent is to be believed, the changes will be much greater than a simple bore and stroke increase.

The new engine design (black) in the patent is more horizontally oriented than the existing NC750 mill (red), and is also more compact. (.Japanese Patent Office/)

Unicam Cylinder Head

Overlay the outline of the engine shown in the new patent and the existing NC750 motor and it’s instantly clear the two designs share little, apart from their general layout.

The new design appears to be intended to lie flatter than the current one, with the cylinders running almost parallel with the ground. That change would increase the already substantial storage space above the engine in the NC range of bikes but, given an increased displacement, could also pose a packaging problem, with the cylinder head invading the space needed for the radiator—or even interfering with the front wheel when the fork compresses. Honda’s solution is to make the cylinder head more compact, and the patent illustrations show the new engine featuring the Unicam layout that first appeared on the CRF450R back in 2002.

Instead of the camshaft being under the rocker arms, the Unicam design (seen here on the CRF450R) places it above the intake valves. (Honda /)

While the existing NC750 engine is already a single overhead cam design using rockers to operate four valves per cylinder, the Unicam achieves the same goal but takes up less space. Instead of having the camshaft underneath the rocker arms in the center of the cylinder head, it puts it directly above the intake valves. That means it operates directly on the intake valves, rather like a DOHC camshaft would, while additional exhaust lobes act on triangular rockers to operate the exhaust valves.

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The result is a cylinder head that’s shorter overall than a typical SOHC design, and one that’s particularly compact on the exhaust side of the head. What’s more, it allows for a tighter included valve angle, making the head narrower and allowing for a flatter combustion chamber for a higher compression ratio. Unicam has already been used to great effect on the CRF450R, which demonstrates its DOHC-style performance potential, and on the VFR1200. It’s also a feature of the latest Africa Twin.

The Unicam layout is also in use on the VFR1200. It takes up less space and is more compact on the exhaust side of the head than the existing NC750 engine. (Honda /)

More Compact Transmission

Like the current NC750, a key feature of the new design is Honda’s dual-clutch DCT transmission, which allows for seamless up- and downshifts at the touch of a button or even automatically, without a momentary loss of drive. This gearbox works just like the firm’s other DCT designs; the input shaft is split into two halves, one carrying first, third, and fifth gears, and the other bearing second, fourth, and sixth.

With a clutch for each half of the input shaft, two gears are selected at any one time, but only one clutch is engaged. Changing gear is thus simply a case of disengaging the first clutch and engaging the second.

While none of this is new, the aspect that Honda’s latest document appears to be trying to patent is a built-in hydraulic actuator for the gearbox, replacing the usual separate actuator. Unlike the existing NC750 DCT, which has its actuator unit bolted to the side of the gearbox, the new design features one that’s integrated into the top of the transmission, making it more compact overall.

Any replacement for the NC range will need to be adaptable to a host of different applications, from scooter to adventure bike. (Japanese Patent Office/)

Key To A Host Of New Models

The original NC700—launched in 2012—and the updated NC750 that followed two years later have become the building blocks of a surprisingly wide array of bikes. Along with the NC750S naked streetbike and NC750X adventure model, the Integra scooter is based on the same engine and chassis. Honda’s CTX700 and CTX700N cruisers are also spin-offs using many of the same components including much of the same engine and frame design. Wilder variations on the theme have included the sci-fi-styled NM4 Vultus and hard-to-classify X-ADV, which sits all alone as the world’s only adventure-inspired 750cc scooter. Any replacement for the NC750 therefore has a lot of roles to fill, as the same engine and chassis is likely to be used in successors to all those machines.

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Speaking of the chassis, although Honda’s patent shows the new engine in the old NC’s tubular steel frame, it’s clearly not designed to fit there. The engine mounts don’t line up and the new engine is obviously intended to be mounted more horizontally. That means when we do get to see the bike this engine is really designed for, it will feature a completely different frame design.

The engine’s suggested 850cc capacity combined with its parallel-twin layout and the Unicam cylinder head also mean it could be related to the “baby” Africa Twin model that’s the subject of a growing number of rumors. While a smaller AT makes sense, particularly given the existence of rivals like Yamaha’s Ténéré 700, BMW’s F 850 GS, and KTM’s 790 Adventure, Honda doesn’t currently have a suitable engine to power it.

Could a bigger, more rugged NC850X be better positioned to compete against the Ténéré and BMW F 850 GS? (American Honda/)

One solution could be to give the replacement for the NC750X, one of the bikes this engine is likely to be destined for, a more rugged appearance and greater off-road ability with wire wheels and longer-travel suspension.

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