The Buell 1125R is a sport bike that was made by Buell Motorcycle Company in the United States. It was introduced in July 2007 for the 2008 model year. Production of road-going 1125Rs, and all Buell models, ceased in October 2009. In November 2009, Buell founder Erik Buell launched Erik Buell Racing, which initially produced race-only versions of the 1125R.^[5]

The 1125R is powered by a 1,125 cc (68.7 cu in) Helicon V-twin engine made by BRP-Powertrain (Rotax) of Austria. The liquid-cooled engine has a V angle of 72° and produces a claimed 146 hp (109 kW), with a rpm limit of 10,500.^[6] Motorcycle Consumer News tested 127.1 hp (94.8 kW) and 71.1 lbf⋅ft (96.4 N⋅m) at the rear wheel,^[1] while Cycle World reported 134.0 hp (99.9 kW) @ 9,800 rpm and 75.9 lbf⋅ft (102.9 N⋅m)} @ 8,300 rpm.^[2] The two magazines reported top speeds of 158 and 161 mph (254 and 259 km/h) respectively, and 0 to 1⁄4 mile (0.00 to 0.40 km) times of 10.51 and 10.39 seconds at 134.32 and 134.09 mph (216.17 and 215.80 km/h).^[1][2]

The Helicon engine's 72° layout differs from Buell's previous V-twins, which were based on 45° air-cooled Harley-Davidson Sportster motors, modified for greater efficiency and output.

The 1125R includes a number of unconventional design attributes. The patented frame design houses the bike's fuel. The single, eight-piston front brake, called ZTL2, has a 375 mm (14.8 in) inverted rotor that is directly attached to the front wheel rim. This enabled Buell to design a front end that was lighter and more responsive than traditional designs. The bike also uses an exhaust under the engine for greater volume. The frame, front end and exhaust all contribute to Buell's main design aim of mass centralization. Instead of a drive chain the 1125R uses a drive belt, which does not require lubrication or adjustment.