Wossner 8784DA Piston Kit - 2004-2025 Yamaha YFZ450 YFZ450R YFZ450X Size A

Wossner 8784DA Pro Series Forged 4-Stroke Piston Kit - Standard Size A

Reclaim the podium with the Wossner 8784DA Piston Kit, the ultimate performance upgrade for the Yamaha YFZ450 series. Engineered to fit a massive range of Yamaha sport ATVs from 2004 through 2025, this "Size A" forged kit is the professional choice for riders performing a top-end refresh on new or low-hour cylinders. At Moto-House MX, we know the YFZ450R and YFZ450X are the benchmarks for ATV motocross and woods racing; Wossner’s Pro Series forging provides the structural integrity needed to handle the high-revving demands of both carbureted and EFI Yamaha powerplants.

The 8784DA features a high-performance double-bridged forging design that offers incredible strength while remaining exceptionally lightweight. To ensure your engine survives the heat of a 30-minute moto, Wossner has integrated enhanced piston pin oiling slots and radial boss machining for superior wrist pin lubrication. The piston skirt is treated with a permanent coating to reduce friction and minimize piston rock, resulting in a quieter, more efficient engine. Precision-machined for 95.00mm bores, this 94.95mm Size A kit is designed to maintain or slightly enhance your factory compression ratio, providing the punch you need for the holeshot.

Top Features: Wossner 8784DA Piston Kit

• Standard Size A (94.95mm): Precision-engineered for factory 95.00mm bores to provide the tightest possible piston-to-wall clearance for maximum efficiency.
• Pro Series Forging: Advanced double-bridged design provides superior structural integrity and resistance to thermal fatigue under extreme racing conditions.
• Optimized Lubrication: Features enhanced oiling slots and annular grooves to ensure the wrist pin remains lubricated during high-load, high-RPM operation.
• Low-Friction Skirt Coating: Permanent skirt treatment reduces internal drag, protects the cylinder wall, and ensures a smoother break-in period.
• Universal Fitment: Specifically tuned for compatibility with both carbureted (2004-2013) and fuel-injected (2009-2025) YFZ450 models.
• Complete Assembly: Includes the high-performance forged Size A piston, rings, wrist pin, and pin locks.

Expert Pro-Tip: The Yamaha YFZ450 series has evolved significantly over the years, but the 95.00mm bore remains a high-performance standard. When performing your top-end rebuild, always confirm your cylinder is within factory Size A specifications using a precision bore gauge. For a professional-grade installation, always use a fresh top-end gasket kit and utilize premium synthetic oil to protect your forged assembly. Whether you are racing GNCC woods or AMA ATVMX, this forged piston is the most reliable way to maintain peak horsepower.

Fitment List & Compression Specs

Year Range	Vehicle Model	Compression Ratio
2014-2025	YFZ450R / SE	12.5:1 (EFI)
2009-2013	YFZ450R / SE	12.3:1 (EFI)
2010-2011	YFZ450X / SE	12.3:1 (EFI)
2004-2005	YFZ450 / LE	12.6:1 (Carb)
2006-2009	YFZ450 / SE / BB	12.0:1 (Carb)
2012-2013	YFZ450	12.3:1 (Carb)

Frequently Asked Questions

Q: Will this fit both the YFZ450R (Aluminum Frame) and the original YFZ450 (Steel Frame)?
A: Yes, the 8784DA is engineered to fit both the carbureted YFZ450 models and the fuel-injected YFZ450R/X models, making it a highly versatile performance part for Yamaha ATV owners.

Q: Do I need to run race gas with this piston?
A: Most configurations for this piston range between 12.0:1 and 12.6:1 compression. These ratios are generally safe for high-quality 91-93 octane pump gas, though high-altitude or high-load racing may benefit from a race fuel blend.

Q: What is the advantage of the Pro Series forging?
A: The Pro Series double-bridged design is much stronger than a standard "open" skirt piston. It resists the "squishing" or deforming that can happen under the extreme cylinder pressures of a high-performance 4-stroke engine.

Recommended Pairings

• Complete Top End Gasket Set: Vital for ensuring a leak-free rebuild and maintaining the correct squish gap.
• High-Performance Oil Filter: Keep your new forged assembly protected by ensuring clean oil flow from the very first start-up.

Restore your machine’s power and precision today. Buy now at Moto-House MX!

Moto-House MX – Choice of Champions – is located in Clermont/Montverde, FL. The Best Motocross/UTV & ATV Shop in Central Florida. Stop by our local store in Montverde, FL or enjoy lightning-fast shipping across the USA.