For the first time in the Buell line up, a water-cooled engine makes its way in between the massive aluminum frame rails, and it’s not a Harley Davidson sourced unit either. (Photo: Fonzi)
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As a completely new model for 2008, the big news with the 1125R is the engine. For the first time in the Buell line up, a water-cooled engine makes its way in between the massive aluminum frame rails, and it’s not a Harley Davison sourced unit either. Moving away from the air-cooled, 45-degree V-twin power plant for the first time, Buell worked with BRP-Rotax to design a new, high performance, 72-degree, water-cooled, V-twin. As a name you might be familiar with for their work with Aprilia’s big sport bikes, BRP-Rotax has been designing and building engines since 1920
By using a 72-degree cylinder angle, Buell was able to put the engine as far forward as possible, giving the 1125R 54% of its weight distribution on the front wheel. Inherently smooth by virtue of its angle, the engine is further calmed with three internal balance shafts. Worry not, the big V-twin most certainly doesn’t feel like it’s been neutered, as it still shakes, rattles and rolls with enthusiasm the minute you thumb the starter button. It just isn’t enough to spoil the fun. The cylinder capacity was chosen to allow a large 103mm bore, which allows more valve angle for better breathing. The shorter stroke allows
the engine to rev quicker and higher, while also giving better throttle response. From the rider’s perspective this is all to be applauded, as the Buell is smooth and rev hungry up high, while still being blessed with gobs of V-twin torque from way down the range.
As a stress member of the frame, the new engine continues the trend of contributing to a very stiff chassis, something that is a trademark Buell feature. Inside each of the heads there are four valves. Double overhead camshafts open and close them, and a self-adjusting cam chain turns the intake cams. The exhaust cams are opened and closed by a gear drive from the intake cams.
Valve actuation borrows from Formula 1, with “finger followers” that use shims for adjustment. This system is said to reduce friction and allows a steep valve angle and downdraft fuel injection. With Buell’s air-cooled models the fuel delivery is often the weakest point of the motorcycle, I am happy to report the DDF13 EFI on the 1125R rocks. Delivering the correct amount of fuel whenever you need it, the system performed flawlessly throughout my test. Do bear in mind here that I didn’t get a chance to try the bike on the road.
