This R1200S might be the most significant racing BMW of the last half-century. The German marque's preparing and entering this bike in the 2007 World endurance Championship marks a significant milestone-the return to world championship roadracing with a factory team after a very long absence. How long? Not since 1957, when Walter Zeller finished sixth in the 500cc Grands Prix, has BMW run its own factory roadrace operation.
Ok, so it's not the oft-rumored MotoGP entry, or even a World Superbike effort, but entering four 24-hour endurance races with a special twin-cam version of its strong-selling R1200S streetbike still represents a serious effort by BMW to reacquaint itself with the rigors of racing.
The team's debut came at the Le Mans 24-Hour last april, where German teammates Thomas Hintereiter, Rico Penzkofer and Markus Barth finished 16th overall against a field of faster four-cylinder Japanese machines and won the Open class for non-homologated bikes (1200cc twins are not yet included in the Superbike or Sport Production categories). a month later at Oschersleben, a second bike ridden by Brit Richard Cooper, German ex-GP star Peter Oettl and Spaniard Jose-Luis Nion joined the first, and both finished in the top 10 overall, placing 1-2 in the Open class. a very credible debut for europe's largest motorcycle manufacturer.
Such success is a credit to BMW's engineering team, led by Rainer Baumel. They worked hard to extract max power from the 1170cc air/oil-cooled flat-twin without sacri- ficing reliability. The biggest changes were to the four-valve cylinder heads, where an all-new double-overhead cam design replaces the streetbike's single high-cam format. Bigger 39mm intake valves (3mm larger than stock) and 33mm exhausts (2mm larger) are now positioned radially at an angle of 11 degrees for max efficiency. Improved breathing, enhanced combustion and extra mixture swirl from the radial valves mean the streetbike's dual ignition is no longer necessary, and there's just one centrally located sparkplug per cylinder. Heads are ported and flowed to suit, then plumbed for improved oil cooling with an accessory oil cooler mounted in the bike's nose to dispose of extra heat.
The R1200S engine now delivers an alleged 140 bhp at 8750 rpm. The Bosch BMS-k eCU has just one engine map controlling a single injector in each 52mm Dell'Orto throttle body. "We didn't have time to try twin injectors, which will give us more performance," says Bumel. "We'll for sure try them in '08."
The stock six-speed Getrag transmission is retained, but with helical gears for smoother operation and a Formula 1-derived gearselection system incorporating sleeves and rollers in place of conventional shift forks. The single-plate, diaphragm-type dry clutch and Paralever shaft drive are identical to the streetbike's, though the team has a choice of cardan units with different final-drive ratios to alter the gearing. Braking is left to a pair of four-piston, radially mounted (a first for the Telelever) Brembo monobloc calipers matched to a single-piston rear that, according to Bumel, none of the riders use.
The endurance racer has essentially the same chassis as an R1200S streetbike, but with a lighter, self-supporting carbon-fiber seat eliminating the road bike's aluminum subframe. The Telelever front end works a fully adjustable hlins shock, with the Marzocchi-made telescopic struts spaced 24mm farther apart on special triple clamps to make room for the quick-change wheel. "We manage to add 23 litres (6 gal.) of fuel and change both tires as well as the rider in only 17 seconds," Bumel says. Front and rear hlins shocks are lengthened 20mm for extra cornering clearance.
The 399-pound (claimed) dry weight of the endurance racer is achieved through an allcarbon- fiber body and lightweight PVM forged wheels, the rear aluminum and the front magnesium (more fragile in a crash but used to lighten steering and reduce rider fatigue).