Rubber-mounted vs solid-mounted engine

A rubber-mounted engine is attached to the frame through rubber bushes or isolators. They absorb much of the engine's vibration, so the rider feels less buzzing in the bars, pegs and seat. Large V-twins and some big singles and parallel twins often use this method.

A solid-mounted engine is bolted directly to the frame. This is lighter and stiffer, and lets the engine act as a stressed member that adds strength to the chassis, which is why it is common on sport and off-road bikes. Smooth-running engines with balance shafts can be solid-mounted without much discomfort.

Worn or cracked rubber mounts increase vibration and can let the engine move, affecting chain alignment. Inspect them during major services.