Vortex 639ZK-51 Black Aluminum Rear Sprocket 51-Tooth

The Vortex 639ZK-51 is a 51-tooth black anodized aluminum rear sprocket engineered for performance street and track riders. Precision-manufactured by Vortex Racing in the USA, this sprocket delivers reliable power transfer and a meaningful reduction in rotating mass compared to OEM steel sprockets.

Key Features:

• 51-Tooth Count – Provides increased low-end torque and improved acceleration versus stock gearing
• Black Anodized Finish (ZK) – Hard-coat anodizing offers corrosion resistance and an aggressive appearance
• CNC-Machined Aluminum Construction – Aerospace-grade aluminum reduces rotating mass for improved throttle response
• Lightening Holes – Strategic cutouts further reduce unsprung weight without sacrificing structural integrity
• Precise Tolerances – Manufactured to exact concentricity specs for smooth, quiet chain engagement
• USA Made – Produced by Vortex Racing, a U.S.-based manufacturer with a proven track record in motorsport

The 639ZK-51 is a direct bolt-on replacement designed to work with the correct chain pitch for its application. Whether upgrading for spirited street riding or fine-tuning gearing for the track, this Vortex rear sprocket is a trusted choice among performance motorcycle riders.