Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/127996
years ago - that, and to add the counterbalancer, which removed some, though not all, of the vibration from the SOHC four-valve LC4 motor. This engine began life back in 1986 in 550cc form, weighing under 70 pounds (including carburetor), and was a lesson to all other four-stroke single engine builders on how to deliver usable power without excessive weight - poke, without pork. Chief engineer WoUgang Felber's own title-winning KTM road racer was the first Supermono to tip the scales at under 220 pounds, and that philosophy still holds good on the Duke II today. In spite of a host of improvements, the new bike weighs in at just over 4 pounds more than its predecessor, 319 pounds dry. That is due to a lightweight motor which still scales at 83.6 pounds complete in spite of having added the electric start, a bigger piston and valves, the balance shaft, a second oil pump, beefed-up gear pinions, and lots of sound-dampening rubber - oh, and a bigger BST40 Mikuni carbo Yamaha has rightly been given lots of credit for rewriting the rule book of fourstroke MX-/enduro engine design with the YZ400F,. but KTM was there first a decade ago with a bigger-capacity version that's also street-friendly. The Duke II continues to benefit from that philosophy. The 640 engine in the new model is unchanged from Duke I guise, according to Felber, apart from a larger airbox and all-new anodized exhaust with twin Niro silencers under the seat in 916enduro style. These work on the resonance principle and are mainly responsible for the 10-percent hike in power compared to the old bike, with 55 bhp now on tap at 7200 rpm. Largely unchanged, too, is the chrome-moly tubular-steel chassis, which has a new, stiffer, polished-alloy swingarrn (but the same linkage for the WP rear shock), and with 43mm WP upside-down forks replacing the old 40mm numbers. The forks are 20-percent stiffer.on compression damping than the same front end on the Supermono bike, says Felber, giving more tarmac-friendly handling. Latest-spec Brembo brake hard ware (a single 320mm front disc and four-pot cali per, as before, with a 220mm rear) is Fun, fun, fun: The torquey four-stroke single and nimble-handling chassis entices thrill-seekers to push the bike hard, making it a hooligan bike of the highest magnitude. now mounted to the new-generation BBS cast-alloy thin-spoke wheels developed in Supermono road racing by the MuZ works team, which, unlike the wire wheels on the Duke I, allow tubeless BT92 Bridgestones to be fitted, in turn reducing unsprung weight. They look nice, too - though in the more, er, vivid of the two color schemes, a lime-green-and-black combo with the wheels painted black as well. Some 555 examples of the "godawful green god- 17