394M08700 Wiseco .080 Piston Kit for Yamaha IT400 YZ400 1977-1978 87mm

Wiseco .080 Piston Kit for Yamaha IT400 & YZ400

This Wiseco .080 oversize piston kit for Yamaha IT400 and YZ400 restores top-end compression on 1977-1978 models, with OEM cross-reference 394M08700 at an 87.00 mm bore.

Overview

This Wiseco .080 piston kit for Yamaha IT400 and YZ400 is a forged oversize top-end solution for worn or scored cylinders that have been bored to 87.00 mm. The kit for Yamaha IT400 and YZ400 delivers the durability and consistent ring seal demanded on two-stroke singles, and the 394M08700 cross-reference helps confirm correct fitment.

Built For Performance

• Forged high-silicon aluminum construction for strength under two-stroke combustion loads
• .080 oversize at 87.00 mm bore to clean up worn or damaged cylinder walls
• Precision-machined ring grooves for consistent ring seal and stable compression
• OEM cross-reference 394M08700 for fitment verification
• Kit format supplies piston, rings, wrist pin, and circlips for a complete top-end rebuild
• Designed to match the port timing and dome profile of the 400cc two-stroke engine

Fits These Machines

• for Yamaha IT400 1977-1978
• for Yamaha YZ400 1977-1978

On-The-Job Use

• Top-end rebuild after a seize or loss of compression
• Cylinder boring and honing to the .080 oversize
• Vintage motocross and enduro engine refresh
• Restoration of 1977-1978 400cc two-stroke machines

Specs At A Glance

Good To Know

Q: Does this kit require cylinder machining? A: Yes, the .080 oversize piston needs the cylinder bored and honed to 87.00 mm with the correct clearance for a proper ring seal.

Q: Is this an original Yamaha part? A: No, this is an aftermarket Wiseco piston kit for Yamaha IT400 and YZ400 applications, referenced by OEM number 394M08700 for fitment matching.

Slight variation in finish or dimensions may occur between production runs, and fit can depend on serial number, so confirm compatibility before ordering.