520-104 O-Ring Drive Chain for Yamaha YZ125 1977-1979

520-104 O-Ring Drive Chain for Yamaha YZ125

This 520-104 O-ring drive chain is a direct replacement chain that transfers engine power to the rear wheel on Yamaha YZ125 models from 1977 through 1979.

Overview

The 520-104 O-Ring Drive Chain is built to replace a worn or stretched chain on Yamaha YZ125 machines from the 1977 to 1979 model years. Each O-ring seal holds grease at the pins and rollers to reduce friction and slow wear. Riders rebuilding a vintage YZ125 drivetrain get a fresh chain sized at 104 links.

Built For Performance

• O-ring seals between plates retain grease and block grit
• 520 pitch matches the YZ125 sprocket spacing
• 104 link count sized to fit the YZ125 swingarm and gearing
• Roller design spreads load across the rear sprocket teeth
• Sealed construction cuts friction and extends chain service life

Fits These Machines

• for Yamaha YZ125, 1977
• for Yamaha YZ125, 1978
• for Yamaha YZ125, 1979

On-The-Job Use

• Trail riding and woods loops on vintage two-strokes
• Motocross practice and race day chain replacement
• Full drivetrain rebuilds when sprockets and chain are swapped together
• Restoration projects bringing a 1970s YZ125 back to riding condition

Specs At A Glance

Good To Know

Q: How do I know if my YZ125 needs a new O-ring drive chain? A: Check for tight spots, rusted links, or a chain that no longer holds adjustment. A stretched chain will hang loose off the rear sprocket teeth and should be replaced.

Q: Should sprockets be replaced at the same time as this drive chain? A: Yes, worn sprocket teeth accelerate chain stretch and can cause rapid failure. Replacing the chain and sprockets together protects the new chain and keeps wear even.

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