Last September, CFMOTO surprised us by revealing disguised prototypes of two new sports bikes, the 675RR and the 500SR, the first with a 675cc three-cylinder engine and the second with a 600cc four-cylinder engine. Now, the company has filed patent applications related to the 500SR engine to give us the first look at its internals.
Although CFMOTO showed the 675SR’s 675cc three-cylinder engine at EICMA last November, confirming its layout and offering some vague performance claims, including a power output of around 100 hp at 12,300 rpm. The 500SR remains a mystery. A prototype took some public demonstration laps on a track in China last year, alongside the 675SR – both bikes heavily disguised with camouflage to keep technical details and styling hidden – but other than revealing that the bike sounds as loud as expected from a 500cc bike, little was disclosed.
The new patent applications focus on some common elements of the engine, centering on a cooling system designed to bring the engine to operating temperature as quickly as possible, likely to help meet increasingly strict emissions limits that include cold start tests. However, the documents include engine diagrams that give us a clear view of its layout and internal components.
The images clearly show that the engine was designed by CFMOTO – after all, there aren’t many modern 500 cc inline engines on the market, even if the company wanted to copy a rival – and that it is a very conventional and high-performance four-cylinder engine. Details include dual overhead camshafts chain-driven, with the chain at one end of the crankshaft instead of in the center. We can also see that there are four valves per cylinder and coil-on-plug electronic ignition.
There is a conventional six-speed transmission – last year’s prototype may have been disguised, but the clutch and gear lever were clearly visible, so there is no semi-automatic trick here – and a wet sump that is offset to allow space for the exhaust system to pass underneath.
Regarding performance, we can logically expect the 500SR to sit below the 675SR in CFMOTO’s power pyramid, between the over 100 hp three-cylinder and the 449cc, 50 hp 450SR twin. As a direct rival to the small fours, including Kawasaki’s Ninja ZX-4RR and Kove’s 450RR, CFMOTO will aim to achieve around 80 hp from the 500SR.
When launched later this year, the 500SR will be another step in the unexpected revival of small capacity fours, a class that seemed doomed by tight emission regulations and the trend towards cheaper to manufacture twin-cylinder engines.
Source: https://www.cycleworld.com
