In an era when motorcycle manufacturers spend fortunes developing race-replica motorcycles more suited to the racetrack than the road, Kawasaki leads the way in the affordable middleweight class with their lively 650cc parallel-twins as used in the ER-6f, ER-6n, Versys 650 and Vulcan S motorcycles.
A few decades ago a 650cc four-stroke parallel-twin with perhaps 50 horsepower – think Triumph Bonneville and BSA Lightning – was just the business amongst big-bike fans but the engine format slid virtually into obscurity as the four-cylinder engine layout gained popularity. The old British air-cooled engines were by modern standards absolute dinosaurs though, with pushrod-operated valve gear, air-cooling, finicky contact-points ignition, pernickety carburettors, oil leaks galore and 3600 crankshafts that saw both pistons thumping up and down the barrels together. For their 21st Century twins Kawasaki worked upon the premise that a liquid cooled 650cc fuel-injected and liquid-cooled dual-overhead-camshaft 1800 parallel twin with four valves per cylinder and balance shafts could deliver excellent performance and reliability in a compact, lightweight, affordable and reliable package that delivered more power than most riders honestly need. With American motorcycle magazines recording standing quarter-mile (400 metre) times of 12 seconds and 0-100 km/h times of less than four seconds for the production bikes straight out of the box, the Japanese manufacturer’s confidence proved well-founded. Those times would surprise many a modern Supercar owner and in reality aren’t a quantum leap behind the acceleration times of some 1000cc superbikes costing more than double the price. Suitable for beginners and women only? Not so. Although the Kawasaki twins are more comfortable and easier to ride for novices, they’ve proven very popular with experienced riders who’re tired of paying for 300 km/h top speeds that they never use.
What has surprised many, though, is the way the underrated 650 twins have taken to tuning and how successful they’ve proven in widely disparate forms of motorcycle racing, from Grand National flat-track racing in the USA to pure road racing at the Isle of Man TT. In the USA the Japanese twin is seriously challenging and often beating the Harley-Davidson XR750s that have so long ruled the roost in the American Motorcycle Association’s top (GNC1 Twins) class on the mile and half-mile ovals. In fact, Kawasaki won the AMA Pro Flat Track Manufacturer of the Year Award in 2012 and 2014. (SEE HERE)
It’s also interesting to see Cycle World’s take on why the newcomer is giving the 750 Harley, that’s enjoyed 44 years of development for flat track racing, such a run for its money. (SEE HERE)
The Isle of Man TT races have long featured a Lightweight race that in different eras pitted exotic works 125cc or 250cc Grand Prix machinery (depending upon the year of the event) against their peers. The current formula is for 650cc twin-cylinder four-stroke production-based machines, and there is a strict limitation upon modifications that may be carried out. Crankshafts, cylinder heads, valves, frames and swingarms must come from production bikes, although some adaptations are allowed, and the standard rev-limiter that came with the production machine may not be tampered with. Kawasaki has dominated the class since its inception with their twins and from 2012 to 2014 the top ten finishers were all mounted on Kawasaki ER-6f machinery. This year nine of the top ten racers were on Kawasakis, with the sole exception being Michael Rutter who finished third on an exotic Italian Paton production racer that uses a Kawasaki 650cc twin engine in a very trick frame. Ivan Lintin won the four-lap race at an average speed of 118.936 miles per hour and James Hillier set a new class lap record of the 60 km circuit at an average of 120.848 mph – that’s an almost 195 km/h average over 60 km of public roads on a road-based Kawasaki 650 twin. Top speeds are around 260 km/h which is astonishing for any twin-cylinder four-stroke middleweight machine, let alone one based upon a very affordable street bike often dismissed as being suitable mainly for “novices and women”!
Story by: Gavin Foster
Photo by: Samantha Blankenship