516655 Lining, primary chain adjuster

This MCS primary chain adjuster lining is a critical wear item for late 1958 to early 1980 XL Sportster models. It is designed to replace OEM 39978-58. The lining provides a smooth, durable surface for the primary chain to ride on, preventing metal-on-metal contact and reducing noise within the primary case. Over time, the chain will wear a groove into this lining, which can lead to improper chain tension and potential damage if left unchecked. Replacing this lining during your regular primary service is a cheap way to ensure your Sportster's drivetrain remains quiet and your chain stays properly tensioned for years to come.