WOSSNER K8877D500-2 Polaris RZR Ranger 800 Big Bore Forged Piston Kit +5.00mm

Unleash Twin-Cylinder Torque with the K8877D500-2 Big Bore Kit

Transform your Polaris 800cc engine with the professional-grade engineering of the WOSSNER K8877D500-2 Piston Kit. This +5.00mm oversize (85mm bore) forged twin-piston set is specifically designed for the high-torque demands of the Polaris RZR, Ranger, and Sportsman 800. Whether you are rebuilding a tired utility workhorse or a trail-shredding RZR, these pistons provide a substantial strength upgrade over stock cast components. Forged from aerospace-grade aluminum, this kit ensures your parallel-twin engine runs cooler and more reliably during the most intense riding sessions. Available now at Moto-House MX—the leader in high-performance UTV engine solutions.

The technical precision of the K8877D500-2 is built for longevity and efficient power delivery. Featuring advanced radial boss machining and enhanced oiling slots, these pistons ensure the wrist pins stay perfectly lubricated even under high-load conditions. The skirts are treated with a specialized dry-film coating to minimize friction and prevent scuffing, while the ring lands are reinforced for superior oil control and a rock-solid seal. With a precision-engineered 12.0:1 compression ratio, this kit maximizes combustion efficiency while maintaining compatibility with premium fuels. This complete dual-piston set includes everything required for a professional top-end restoration: two forged pistons, high-tension rings, wrist pins, and heavy-duty pin locks.

Top Features: WOSSNER K8877D500-2 Twin Piston Kit

• Balanced Twin-Cylinder Set: Includes two matched forged pistons designed specifically for the Polaris 800cc parallel-twin engine.
• +5.00mm Big Bore (85mm): The ultimate solution for rescuing worn cylinder blocks and significantly increasing engine displacement.
• Advanced Pin Lubrication: Radial boss machining and annular grooves optimize oil flow to protect wrist pins during high-stress operation.
• Anti-Friction Skirt Coating: Advanced dry-lubricant coating reduces "piston rock" and engine noise for a smoother-running machine.
• Aerospace Forged Alloy: Superior strength-to-weight ratio compared to OEM cast pistons, perfect for heavy-duty UTV and ATV use.

Expert Pro-Tip

A +5.00mm overbore is a significant displacement increase. When installing this kit, we strongly recommend a professional cylinder boring and honing service to ensure exact tolerances, and consider a fuel controller to optimize your mapping for the increased air and fuel demand.

Fitment List

Year Range	Vehicle Brand	Vehicle Model & Size
2008-2014	Polaris	RZR 800 / RZR S / RZR 4 / EPS (All Models)
2009-2014	Polaris	Ranger 800 EFI / Crew / HD / Mid-Size
2005-2014	Polaris	Sportsman 800 EFI / Big Boss / MV / Forest
2012-2017	Polaris	Ranger 6x6 800

Frequently Asked Questions

Q: Is this a complete kit for both cylinders?
A: Yes, the K8877D500-2 is a complete twin-cylinder kit including two pistons and all necessary hardware for a full 800cc rebuild.

Q: Do I need to bore my cylinders for this kit?
A: Yes, this is a +5.00mm oversize kit. Your engine block must be bored out to 85.00mm to accommodate these high-performance pistons.

Q: Can I use standard pump gas with the 12.0:1 compression ratio?
A: We recommend using high-octane premium pump gas to prevent detonation and ensure the best performance from this high-compression setup.

Recommended Pairings: Polaris 800 Top-End Gasket Set, High-Performance Main Bearings, and 4-Stroke Synthetic Engine Oil.

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Moto-House MX – Choice of Champions – is located in Clermont/Montverde, FL. The Best Motocross/UTV & ATV Shop in Central Florida.