Wiseco 4045M08850 Forged Piston Kit Yamaha CR Oversize - XT/TT/SR500 88.50mm 10 1 1.50mm

The Wiseco 4045M08850 is a forged high-performance piston kit designed for the classic Yamaha single-cylinder 500cc platform. This kit features an 88.50mm actual bore diameter — a 1.50mm oversize over the standard 87.00mm bore — and delivers a 10:1 compression ratio for improved power output over the stock configuration. Cylinder boring is required prior to installation.

Constructed from high-silicon aluminum alloy, the Wiseco forged piston offers superior tensile strength and an optimized strength-to-weight ratio compared to cast alternatives. The dedicated forging design and precision piston skirt geometry are engineered to maximize both horsepower and torque while extending service life. All Wiseco 4-stroke pistons are engineered, forged, and machined in the USA in Mentor, Ohio, and built to tight tolerances for consistent performance.

Kit Includes:

• 3484XC — 88.50mm ring set
• S553 — 20mm wrist pin (2.185 in. length)
• CW20 — Round wire wrist pin locks, 20mm (pair)

Specifications:

• Bore — Standard: 87.00mm
• Bore — Actual: 88.50mm (1.50mm oversize)
• Stroke: 84.00mm
• Displacement: 508cc
• Compression Ratio: 10:1
• Wrist Pin Diameter: 20mm

Important: This is an oversize piston — cylinder boring to 88.50mm is required before installation. This kit is designed for the Yamaha TT500, XT500, and SR500 (1976–1981 model years).