CFMoto 500SR Four-cylinder Appears in Patents

[Hugh Janus]

We speculate that CFMoto’s 500cc four will produce around 80 hp. (CFMoto/)

Last September CFMoto surprised us by unveiling disguised prototypes of two new sportbikes, the 675RR and 500SR, the former a 675cc three-cylinder and the latter a 600cc four-cylinder. Now the company has filed patent applications related to the 500SR’s engine to give our first glimpse of what’s inside.

The disguised CFMoto 675RR. (CFMoto/)

Although CFMoto went on to show the 675cc triple that featured in the 675SR at EICMA last November, confirming its layout and offering some vague performance claims including a power figure that will be somewhere north of 100 hp with a 12,300 rpm redline. The 500SR is still more of a mystery. A prototype made some public demo laps of a track in China last year alongside the 675SR—with both bikes heavily disguised with camouflage wraps to keep the technical details and styling hidden—but apart from revealing that it screams just as much as you’d expect from a 500cc four, little was revealed.

Related: A Swan Song for the Inline-four Sportbike?

This first glimpse of the 500SR was released last September. (CFMoto/)

The new patent applications relate to some mundane elements of the engine, focusing on a cooling system that’s intended to get the motor up to operating temperature as rapidly as possible, probably to help meet increasingly tough emissions limits that include cold-start tests. However, the documents include blown-apart diagrams of the motor that give us a clear look at its layout and internals.

The patent is related to the engine’s cooling system. (CFMoto/)

It’s clear from the pictures that the engine is CFMoto’s own design—after all, there aren’t many modern 500cc inline-fours on the market, even if the company wanted to copy a rival—and that it’s a fairly conventional, high-performance four. Details include chain-driven double-overhead camshafts, with the chain on one end of the crank rather than being central. We can also see that there are four valves per cylinder, with bucket tappets rather than finger followers, and coil-on-plug electronic ignition.

There’s a conventional six-speed transmission—last year’s prototype might have been disguised, but the clutch and shifter were clearly on display, so there’s no semi-auto trickery here—and a wet sump that’s offset to allow space for the exhaust system to pass underneath.

This cool exploded view of the 500cc inline-four gives us a ton of information. (CFMoto/)

When it comes to performance, we can logically expect the 500SR to sit below the 675SR in CFMoto’s pyramid of power, sliding between that 100-hp-plus triple and the 50-hp, 449cc 450SR twin (which is sold under the name 450SS in the US). As a direct rival to small fours including Kawasaki’s Ninja ZX-4RR and Kove’s 450RR, CFMoto will be looking to get around 80 hp from the 500SR.

Another view of the 500SR. (CFMoto/)

The bike itself adopts the same sort of street-biased sportbike design as the Ninja ZX-4RR, with clip-on bars that are a little higher than those of an out-and-out supersport machine. The nose bodywork and tank are both cut away to give more steering lock than you might normally expect, and there’s a particular focus on aerodynamics including cowls around the front brake rotors to funnel air to the calipers, plus disclike covers on the rear wheel to clean up airflow at the back. Radial-mount brakes, an upside-down fork, a belly-mounted exhaust system, and a high, stubby tail that looks like torture for pillions.

When launched later this year the 500SR will be another step in the unexpected revival for small-capacity fours, a class that seemed to be doomed by tight emissions rules and the trend toward cheaper-to-manufacture parallel twins.

The Kawasaki ZX-4RR may have some future competition. (Kawasaki/)

Source

[Buckster]