Hammerhead Big Bore 61mm (171cc) Engine Rebuild Kit with Cylinder and Top End for 150cc, GY6

Hammerhead Big Bore 61mm / 171cc Engine Rebuild Kit with complete head assembly and top end kit. The Hammerhead 61mm Big Bore Kit is the only 171cc upgrade available in the U.S. designed to fit without machining your engine cases. Featuring a specialized 62.9mm outer skirt, this aluminum cylinder drops directly into standard GY6 150cc engines. It is the best bang for the buck for riders demanding a massive jump in torque and acceleration without the need for professional machine shop services.

Hammerhead Big Bore 61mm / 171cc Engine REBUILD Kit includes:

• Complete head assy with valves, everything assembled ready to bolt on and go
• Piston cylinder kit
• cylinder
• piston
• rings
• 2-clips
• pin
• complete set of gaskets

The HammerHead Performance Advantage

• True Bolt-On Engineering: Slim-skirt design eliminates the need to "split the cases" or grind the engine block for clearance.
• Advanced Thermal Cooling: All-aluminum construction dissipates heat significantly faster than stock cast-iron cylinders, preventing power fade during long-distance riding.
• High-RPM Piston: Includes a specialized "short-skirt" racing piston to reduce reciprocating mass, allowing for faster revving and higher top-end potential.
• Comprehensive Kit: Includes cylinder, piston, rings, wrist pin, clips, and performance gaskets.

Technical Specifications

• Displacement: 171.3cc (61mm Bore)
• Outer Skirt Diameter: 62.99mm (Direct Fit)
• Material: High-Grade Aluminum
• Kit Includes: Cylinder, Piston, Rings, Wrist Pin, Clips, and Performance Gaskets.
• PLEASE NOTE: Usually requires a bigger main jet (125 - 130) for optimal performance.

  This product is intended for off-road use only.

  This product is not intended for use on public roads or land.

  This product is not legal for use in California on pollution-controlled vehicles. Check local laws before installing.