The STIHL MS 651 chainsaw features a 91.1 cm3 engine, 5.0 kW (6.8 bhp) power output, and weighs 7.3 kg (without the guide bar and saw chain). It is designed for professional use, offering a power-to-weight ratio of 1.46 kg/kW, and supports various guide bar lengths from 40 cm to 90 cm. The fuel tank capacity is 0.850 L, and the chain oil capacity is 0.40 L.