Wiseco SK1129 2-Stroke Forged Piston Top End Kit 67.00mm Bore

The Wiseco SK1129 is a precision-matched and balanced 2-stroke forged piston top end kit designed for the Yamaha SS/SS440 snowmobile with a 67.00mm bore. Engineered, forged, and machined entirely in the USA at Wiseco's Mentor, OH facility, this kit delivers the strength and reliability demanded by high-performance snowmobile applications, from snocross racing to cross-country riding.

Wiseco's snowmobile piston kits are built on over 80 years of 2-stroke performance expertise. Because Wiseco controls every step of the manufacturing process—from raw bar stock through skirt coating—each piston is held to exacting tolerances for optimal fit, power output, and service life. In-house dyno testing drives continuous development of advanced piston shapes, coatings, and components.

Key Features:

• 67.00mm bore — precision-matched for the Yamaha SS/SS440 engine
• Forged from high-silicon, low-expansion aluminum alloy for superior strength, reduced weight, and improved heat transfer
• Dedicated forgings with condensed, aligned grain structure for higher mechanical properties and resistance to impact and fatigue
• Lightening operations optimize the strength-to-weight ratio for peak performance
• CNC-machined cam shape and skirt profile tuned for maximum horsepower and service life
• Engineered to maintain proper installed clearance for best seal, least wear, and maximum power at running temperature
• Includes high-quality piston ring(s), wrist pin, and circlips
• Cast iron bore compatibility
• Manufactured in the USA

Compared to cast pistons, Wiseco's forged construction is tougher and more durable, resisting catastrophic failure under extreme loads. The SK1129 kit provides a complete top-end solution, making it ideal for engine rebuilds and performance upgrades on the Yamaha SS440 platform.