Engineered to meet or exceed Yamaha’s performance benchmarks, this OS 0.50 oversize piston kit restores compression and sustained power for Yamaha YFM 660 Grizzly, Rhino, and Raptor models manufactured from 2002 through 2007. The kit is designed to drop into the stock bore with tight, precision tolerances, delivering reliable top-end sealing and improved throttle response. It’s an ideal choice when you’re chasing lost compression from worn rings, bore wear, or consistent power fade after years of trail and farm use.

This aftermarket replacement is precision-machined to restore peak performance in demanding riding conditions. The OS oversize approach helps reclaim lost compression by compensating for bore wear, reducing blow-by, and reestablishing power for difficult climbs, heavy loads, and long days on rough terrain. For trail riders and farm work alike, it offers a dependable, bolt-in solution that revives engine efficiency without resorting to a full engine rebuild.

Comprehensive Vehicle Fitment

Product Specifications

OEM & Aftermarket Cross-Reference Information

What’s Included

This piston kit comes complete with the essential top-end components you need for a proper refresh.

• Piston
• Rings
• Wrist Pin
• Piston Circlips

Why Choose This Aftermarket Replacement?

• Direct-Fit Compatibility – engineered to drop into the stock bore without extensive machining, restoring factory-like performance.
• OEM Cross-Reference – aligns with Yamaha OEM standards for 2C6-11636-00-00 and 3YF-11636-00-00, ensuring reliable interchangeability.
• Premium Materials – forged aluminum piston delivers strength-to-weight advantages and better heat tolerance for demanding trail and work sessions.
• Accurate Oversize Return – OS 0.50 oversize compensates for bore wear, reclaiming compression and steady power delivery.
• Complete Top-End Kit – includes rings, wrist pin, and circlips for a straightforward installation and a smooth break-in.
• Performance Restoration – aimed at reviving lost power and responsiveness after long-term use in rugged conditions.

Installation Notes:

• Verify bore size before installation and confirm you need OS 0.50 oversize; re-bore if the cylinder shows excessive wear beyond tolerance.
• Thoroughly clean the cylinder, honing deposits and scoring before installing rings and the piston; inspect ring grooves for wear.
• Lubricate the piston, rings, and wrist pin with assembly lube or clean engine oil during assembly to prevent dry startup.
• Install rings in the correct orientation and stagger ring gaps to minimize blow-by; use a proper ring compressor for even seating.
• Insert the wrist pin and secure with circlips, ensuring clips are fully seated and not protruding into the oil passage.
• Follow the engine’s service manual for any related gasket replacements and final torque checks on adjacent fasteners; avoid over-tightening bearings or fasteners around the cylinder head.

Why Upgrade?

Running a worn top end on a Yamaha 660 can lead to progressively worse compression, oil consumption, and power loss, especially under load in demanding terrain. This replacement restores reliable compression and consistent power, reducing the risk of piston seizure and unplanned downtime so you can tackle trails or chores with confidence.