871521, Sprag Clutch, Aprilia, Derbi, Moto Guzzi, Vespa, Gilera, Piaggio

A Sprag Clutch with the manufacturer part number of 871521 is a significant component in several automotive brands such as Aprilia, Derbi, Moto Guzzi, Vespa, Gilera, and Piaggio. It's an OEM (Original Equipment Manufacturer) replacement part, meaning it is designed and produced by the same company that originally made that part for the vehicle. An OEM part offers an assured compatibility and quality match with your vehicle.

The main purpose of a Sprag Clutch, also known as a one-way clutch or freewheel clutch, is to allow rotation in one direction and prevent it in the opposite direction. This clutch engages when driven in one direction, but will freely spin without resistance when spun in the opposite direction. This one-way function is vital for many machines, including these mentioned vehicles, to operate correctly.

In the context of automotive applications, a Sprag Clutch can be used in the starter system of an engine, manual transmissions, and some automatic transmissions. In the starter system, it allows the starter motor to be disengaged safely once the engine has started. In transmissions, it contributes to the smooth, seamless shifting of gears.

Apart from its one-way rotation feature, the Sprag Clutch is also recognizable by its unique design. It incorporates a set of “sprags” - the elements, typically shaped like wedges or cams, which lock rotation in one direction. These sprags tilt from a freewheeling position to a locking position, depending on the direction of rotation.

Remember that for maintaining optimal performance and ensuring the longevity of the vehicle's transmission system, it is important to verify the part's compatibility with your specific model before replacement. The manufacturer part number 871521 should be cross-verified with the specific model number of your vehicle. This assures you acquire an accurate and proper fit, preserving the integrity of the overall mechanic system.