Main benefit: This PROX piston kit is made in Japan and engineered as a true OEM replacement—ideal when you want dependable power, correct fitment and long-term durability in an 85cc 2-stroke engine. The piston is cast from a high-silicon aluminum alloy that meets or exceeds OEM specifications and is CNC-machined to extremely close tolerances for consistent sealing and smooth operation.
Whether you’re refreshing a tired top end or doing preventative maintenance before the next race weekend, this complete kit helps you restore compression and throttle response while reducing the risk of premature wear from poor tolerances or low-quality materials.
Key features:
✅ Japan-manufactured OEM replacement design
✅ High-silicon aluminum alloy casting with precision CNC machining
✅ Complete kit supplied with essential installation components
Benefits of use:
🔹 OEM-style fit and tolerances for reliable assembly and performance
🔹 Restores top-end efficiency (sealing/compression) for consistent power delivery
🔹 Convenient all-in-one kit: reduces downtime and missing-parts issues during rebuilds
Technical specifications:
📌 Displacement: 85 cc
📌 Engine type: 2-Stroke
📌 Bore size: 48.50 mm (Standard)
📌 Piston size: 48.46 mm
📌 Skirt coating: Non-coated
📌 Type: Standard Size B
📌 Brand: PROX
📌 Vendor part number: 01.4121.B
Why choose this product?
⭐ Built to OEM standards with Japan manufacturing and tight machining tolerances
⭐ Includes piston, ring kit, wrist pin and circlips—ready for your top-end service
⭐ A smart choice for riders who want reliable performance from a proven replacement kit
