What is the primary control used to adjust speed on a motorcycle?

The primary control used to adjust speed on a motorcycle is the throttle. The throttle controls the engine's power output by regulating the amount of air and fuel that mix for combustion. When a rider twists the throttle grip toward themselves, it opens the throttle valve, which allows more fuel and air into the engine, leading to increased acceleration and speed. Conversely, releasing the throttle decreases the flow, reducing speed.

While the brake is critical for slowing down or stopping, it does not adjust speed in a controlled manner like the throttle. The clutch is used to disengage the engine power from the wheels for shifting gears but does not directly affect speed by itself. The gear shift allows the rider to change transmission gears, which indirectly affects speed but relies on the throttle to control the engine power at a given gear. Therefore, the throttle is specifically designed for speed modulation, making it the primary control for that purpose.