394M08500 Wiseco Std Piston Kit for Yamaha IT400 YZ400 1977-1978 85mm

Wiseco Std Piston Kit for Yamaha IT400 and YZ400

This Wiseco Std Piston Kit, part 394M08500, is an 85.00 mm standard bore piston kit built for the 1977-1978 Yamaha IT400 and YZ400 dirt bikes.

Overview

The Wiseco Std Piston Kit brings stock bore top-end performance back to the 1977-1978 Yamaha IT400 and YZ400. This 85.00 mm piston kit, part 394M08500, replaces worn or damaged pistons without changing the original cylinder bore. It suits vintage dirt bike owners and restorers rebuilding a stock top end for trail and motocross use.

Built For Performance

• 85.00 mm standard bore sizing matched to the stock Yamaha IT400 and YZ400 cylinder
• Wiseco forged piston construction for strength under two-stroke dirt bike loads
• Part number 394M08500 identifies this exact kit for the 1977-1978 IT400 and YZ400
• Complete piston kit format intended for a straightforward top-end rebuild
• Standard bore design keeps the original cylinder dimensions intact

Fits These Machines

• for Yamaha IT400, 1977
• for Yamaha IT400, 1978
• for Yamaha YZ400, 1977
• for Yamaha YZ400, 1978

On-The-Job Use

• Top-end rebuilds on 1977-1978 Yamaha IT400 and YZ400 dirt bikes
• Restoring compression on a stock-bore two-stroke engine
• Vintage dirt bike restoration projects
• Trail riding and motocross engine service

Specs At A Glance

Good To Know

Q: Is this piston kit a standard bore or oversize? A: It is a standard bore kit at 85.00 mm, part 394M08500, made for the stock Yamaha IT400 and YZ400 cylinder.

Q: What should I check before installing it? A: Confirm your machine is a 1977-1978 Yamaha IT400 or YZ400 and that the cylinder is at stock bore before ordering this kit.

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