Namura .040 Over Bore Top End Kit for Polaris Sportsman 850 & Scrambler 850 88mm

Namura .040 Over Bore Top End Kit 88mm for Polaris

This top end kit provides a .040 over bore piston and cylinder assembly for Polaris Sportsman 850 and Scrambler 850 engines using an 88mm bore size.

Overview

The Namura .040 over bore top end kit offers a larger 88mm piston and matching cylinder to restore compression and power in worn Polaris Sportsman 850 and Scrambler 850 ATVs. This top end kit is an ideal solution for engines that require a second oversize rebuild, delivering increased displacement and improved throttle response. This top end kit includes all critical components for a complete top end overhaul.

Built For Performance

• Forged aluminum piston rated for high RPM and heat resistance
• Honed cylinder with cross-hatch finish for optimal ring seating
• Includes piston rings, wrist pin, circlips, and cylinder assembly
• .040 over bore (88mm) provides additional displacement for extra torque
• Designed to match OEM specifications for reliable fit and function

Fits These Machines

• for Polaris Sportsman 850
• for Polaris Scrambler 850

On-The-Job Use

• Rebuilding high-mileage engines after cylinder wear
• Restoring performance in Polaris ATVs used for trail riding
• Utility tasks requiring dependable engine output
• Sport riding and light competition use

Specs At A Glance

Good To Know

Q: Can I use this .040 over bore top end kit on a Polaris Sportsman 850 that has never been rebuilt? A: Only if the cylinder bore is already worn beyond the .020 over size; otherwise, you may need to match the over bore to the existing cylinder condition.

Q: Does this kit include the cylinder head gasket? A: No, the cylinder head and base gaskets are not included and must be purchased separately for a complete rebuild.

Slight variation in finish or dimensions may occur between production runs, and fit can depend on serial number, so confirm compatibility before ordering.