BC0989 – Polaris Pro R (21-up) LW Stroker Kit 78mm w/BC ProH2K Rods

The pursuit of absolute, reliable horsepower in the modern Pro R platform demands an engineered solution, not just an assembled collection of parts. The BC0989 LW Stroker Kit from Brian Crower represents the apex of this philosophy—a complete, precision-balanced system designed to transform the already-potent 2.0L twin-cylinder engine into a torque-monster with uncompromising durability. This 78mm stroker crankshaft, paired with our legendary ProH2K forged connecting rods and high-compression pistons, is the definitive internal upgrade for racers, duners, and performance enthusiasts who refuse to accept compromise. By strategically increasing displacement and optimizing the rotating assembly’s geometry and strength, this kit delivers a profound, across-the-board improvement in power delivery, tractability, and engine longevity, establishing a new benchmark for Pro R performance.

Core Engineering & Design Philosophy

Unlike simple component swaps, the BC0989 is conceived as a synergistic system. The 78mm stroke is a calculated increase over stock, chosen to maximize displacement gains—pushing the engine to approximately 117ci (1916cc)—while maintaining optimal piston speed and cylinder wall loading for sustained high-RPM reliability. The increased stroke fundamentally alters the engine’s volumetric efficiency and torque production curve. However, this gain is only as robust as the components that facilitate it. The kit’s heart is the 4340 chromoly steel stroker crankshaft, precision-machined, micro-polished, and Magnaflux inspected to eliminate stress risers and ensure flawless balance. It is this foundational component that redefines the engine’s breathing characteristics, working in concert with the accompanying rods and pistons to unlock the platform’s true potential.

ProH2K Connecting Rods: The Link to Reliability

The increased stroke and elevated cylinder pressures place immense demands on the connecting rods. Standard or even generic forged rods can become the weak link. This is where BC’s proprietary ProH2K rods separate this kit from all others. Forged from certified 4340 chromoly steel using a state-of-the-art H-beam design, they are engineered for extreme stiffness and fatigue resistance. The “H2K” designation signifies a 2000 MPa tensile strength rating, a threshold that guarantees integrity under the explosive forces of nitrous, forced induction, or sustained high-RPM operation. Each rod is shot-peened for enhanced surface strength, uses ARP 2000 cap screws (the industry gold standard), and is weight-matched to within one gram per set. This obsessive attention to detail ensures not only survival but also a smoother, more balanced rotating assembly that reduces parasitic vibrations and bearing wear.

Performance Benefits & Application

The installation of the BC0989 LW Stroker Kit yields transformative results that are felt immediately. The primary advantage is a massive increase in low-end and mid-range torque. The longer stroke creates greater cylinder filling at lower RPMs, translating to explosive acceleration out of corners, effortless dune climbs, and reduced need to constantly wind out the engine. This torque gain provides a broader, more usable powerband, enhancing vehicle control and responsiveness. When paired with complementary bolt-on upgrades—such as a high-flow intake, performance exhaust, and a proper ECU tune—the stroker foundation allows these components to work far more effectively, often resulting in gains exceeding 25% in peak horsepower and over 30% in torque. For a deeper technical understanding of how stroke impacts engine dynamics, see this resource on stroke-to-bore ratio fundamentals from Engine Labs.

• Substantial Displacement Increase: Bumps engine capacity to ~117ci (1916cc) for a foundational gain in torque and horsepower.
• Unmatched Rotating Assembly Strength: The 4340 chromoly crankshaft and 2000MPa ProH2K rods form an assembly capable of withstanding nitrous, boost, and extreme RPM.
• Optimized Powerband: Dramatically improves low-RPM responsiveness and mid-range pull, making the power more tractable and usable in technical terrain.
• Enhanced Durability: Superior materials and precision balancing reduce internal stress, decreasing bearing wear and increasing overall engine life.
• Complete, Balanced System: Includes pistons, rings, wrist pins, and bearings—all weight-matched and ready for assembly, ensuring optimal balance and reliability.

Technical Specifications & Components

Every component within the BC0989 kit is specified to meet exacting tolerances and material standards. The forged aluminum pistons are designed with the correct compression height for the 78mm stroke and feature a durable skirt coating to reduce friction and noise. They are supplied with high-performance pin-fit rings for optimal seal and heat transfer. All critical clearances—main bearing, rod bearing, piston-to-wall—must be verified during professional installation, as precise assembly is paramount to realizing this kit’s performance and longevity potential.

Vehicle Fitment & Installation Notes

The BC0989 kit is engineered specifically for the modern Polaris Pro R platform. Professional installation by a technician experienced in performance engine building is absolutely mandatory. The process requires complete engine disassembly, thorough cleaning, precise measurement of all clearances (plastigage and micrometer checks are crucial), and meticulous assembly following factory torque sequences and specifications. A performance ECU tune is required to properly calibrate fuel and ignition timing for the increased displacement and compression; running the stock tune will cause detonation and engine failure. This kit is the cornerstone for ultimate NA builds and is also the recommended foundation for forced induction applications seeking maximum reliability.

Primary Fitment:

• Polaris Pro R (All Models and Trims) – 2021, 2022, 2023, 2024+

Conclusion: The Ultimate Internal Upgrade

The Brian Crower BC0989 LW Stroker Kit with ProH2K Rods is not merely an upgrade; it is a strategic re-engineering of the Pro R’s powerplant. It addresses the fundamental levers of performance—displacement, strength, and balance—with components that meet the highest standards of motorsport engineering. For the rider who views their machine as a platform for progression, this kit delivers the authentic, durable power increase that bolt-ons alone can never achieve. It is the definitive choice for building a Pro R that dominates with authority, session after session.