Thursday, November 1, 2012


BMW refurbished its iconic Flat Twin Boxer with a new cylinder head and not an increase in displacement.

The new DOHC radial valve head delivers an extra 5 hp and 3 lb-ft of torque, as well as a 500 rpm higher redline.
It was expected that BMW would debut an upgrade to its iconic Flat Twin Boxer for the 2010 R series. Now the details are revealed, as 2010 motorcycle info leaks prior to the upcoming EICMA Milan Bike Show. Here’s what the spec sheets and PR machine say about the new Boxer.

Same Displacement: No, the Boxer is not gaining any CC. Bore and stroke is identical at 101 x 73mm with the 1170cc displacement unchanged.

New DOHC Cylinder Head: The 2010 Boxer cylinder heads feature cylinder head upgrades first used on the HP2 Sport. The DOHC design sources two chain-driven camshafts, with each camshaft controlling both an intake and exhaust valve in the radial four-valve head. The valves themselves have changed, with diameter increased on both intake (1.42-1.54 inches) and exhaust (1.22-1.30 inches), with valve lift also increased. Compression ratio is unchanged at 12:1, however, a new combustion chamber shape necessitates the use of red-designed cast-aluminum pistons.

Larger Air Intakes: New black throttle butterfly manifolds are larger, up 0.12 inches to 1.97, and work with redesigned intake manifolds and air filter element.

Performance Gains: All the motor tweaks add up to more power and a higher-revving Twin. Peak horsepower claims jump 5 hp to 110 total, with torque up 3 lb-ft to 88. The peak outputs come at a higher rpm, a respective 7750 (up 250 rpm) and 6000 (up 500 rpm). The redline jumps an extra 500 rpm as well, to 8500. Overall, BMW claims the modifications “provide a significantly more homogeneous flow of power and torque throughout the entire speed range.”

Throatier Exhaust: The exhaust system looks identical to its predecessor, but BMW promises a sweeter tune with a new internal structure to the rear can, along with an electronically-controlled exhaust flap. BMW describes the new decibels as “a particularly throaty Boxer sound naturally in full compliance with legal standards.” Naturally.

The new Boxer motor headlines the upgrades to three 2010 R-series machines announced by BMW: the popular BMW R1200GS and its Adventure sibling, as well as the R1200RT tourer.

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