[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.

[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 frame, front end and exhaust all contribute to Buell's main design aim of mass centralization.