BC5917LW – Polaris Pro R (22-up) 78mm LightWeight Stroke Crankshaft

Unleash the True Potential of Your Polaris Pro R with Precision-Engineered Rotational Mass

For the serious builder and competitor, the factory crankshaft is often the final barrier to unlocking the ultimate performance ceiling of the Polaris Pro R platform. Introducing the Brian Crower BC5917LW LightWeight Stroke Crankshaft, a component engineered not as a simple replacement, but as a fundamental upgrade to your engine’s rotating assembly. This 78mm stroker crankshaft is the culmination of advanced metallurgy, precision CNC machining, and race-proven design philosophy. It is engineered for those who demand not just increased displacement, but a transformation in throttle response, power delivery, and overall engine efficiency. By reducing rotational mass while increasing stroke, the BC5917LW delivers a tangible, seat-of-the-pants improvement that translates directly to faster acceleration, reduced engine stress, and superior power under the curve—critical advantages in both high-speed desert running and technical trail domination.

Engineering Excellence: The Core of the BC5917LW Advantage

The BC5917LW is far more than a billet piece of metal; it is a system-critical component designed for symbiotic performance with the Pro R’s potent twin-cylinder engine. Brian Crower starts with premium-grade 4340 chromoly steel billet, renowned for its exceptional strength-to-weight ratio and fatigue resistance. Each crank is then subjected to a proprietary Tuffriding™ thermal diffusion process. This treatment impregnates the surface with nitrogen and carbon, creating an ultra-hard, wear-resistant case that significantly outperforms traditional nitriding. The result is a journal surface with superior lubricity and resistance to micro-welding and scoring, even under extreme pressure and high-RPM operation. Furthermore, the crank’s counterweights are strategically lightened and balanced to exact OEM specifications, ensuring seamless integration without inducing harmful vibrations. This meticulous balancing act—reducing inertia for quicker revs while maintaining perfect harmony—is what sets a true performance component apart from a mere parts-bin special.

Tangible Performance Benefits for the Discerning Driver

• Increased Displacement & Power: The 78mm stroke (over the factory dimension) increases total engine displacement, creating a greater volume for air and fuel combustion. This translates directly to more torque and horsepower across the entire RPM range, with a particularly noticeable gain in mid-range punch.
• Lightweight Rotational Assembly: The “LW” in the part number is critical. Reduced mass in the crankshaft and connecting rods means the engine requires less energy to change rotational speed. This yields exponentially faster throttle response, reduced turbo lag (if applicable), and an engine that feels more lively and connected to your right foot.
• Enhanced Durability & Reliability: Constructed from 4340 chromoly steel and treated with Tuffriding™, the BC5917LW is built to withstand the increased stresses of higher output and aggressive use far better than the stock casting. This is an investment in long-term engine integrity.
• Optimized Engine Efficiency: A lighter, stronger rotating assembly reduces parasitic drag and internal friction. This allows more of the engine’s generated power to be transferred to the drivetrain and wheels, rather than being wasted on moving heavy internal components.
• Race-Ready Out of the Box: Each crankshaft is precision-machined, heat-treated, and balanced to exacting standards. It is a true bolt-in component designed for professional-level builds, requiring no custom clearancing or guesswork for a proper installation when paired with compatible pistons.

Precision Vehicle Fitment & Installation Notes

Vehicle Fitment: This crankshaft is engineered specifically for the 2022 and newer Polaris Pro R model (RZR Pro R 4). Its design is a direct replacement for the OEM crankshaft, ensuring proper alignment with the engine cases, oil pump, and balancer system.

Critical Installation Considerations: While the BC5917LW is a direct-fit component, its increased stroke necessitates the use of compatible pistons to achieve the correct compression height and avoid valve-to-piston interference. It is mandatory to use a piston specifically designed for a 78mm stroke application. We strongly recommend consulting with your engine builder or selecting a matched piston-and-crank kit from Brian Crower. Proper engine assembly, including precise bearing clearance checks and torque-to-yield bolt procedures, is essential to realize the full performance and durability benefits of this component. For a deeper technical understanding of how stroker crankshafts influence engine dynamics, refer to this authoritative resource from Engine Builder Magazine on stroker crankshaft fundamentals.

Technical Specifications: The Brian Crower BC5917LW