Old Britts – Modifying a Pre-MK3 Swingarm for MK3 Lubrication
Download the complete PDF version using the green download button at the top right of this page for an Old Britts technical article covering the modification of a Pre-MK3 Norton Commando swingarm to accept the later MK3 lubrication system. This reference compares the earlier oil-nipple and end-cap arrangement with the improved MK3 felt-wick system, explaining why the later setup provides a cleaner and more self-contained method of lubricating the swingarm bushings.
The article first outlines how the Pre-MK3 swingarm lubrication system works, using an oil nipple, end caps, O-rings and a retaining bolt to hold the assembly together. It then shows the MK3 system, where oil-soaked felt wicks are sealed within the swingarm ends by an oil seal and Welch plug, creating a one-time lubrication arrangement intended to retain oil around the bushings.
The final section explains that upgrading a Pre-MK3 swingarm requires machining the ends to match the MK3 bore. The article gives the MK3 bore specification as 1.261 inches in diameter and .3 inch deep, shows the difference between the Pre-MK3 and MK3 swingarm ends and notes that the shorter MK3 bushings require the matching MK3 swingarm spindle as part of the conversion.
Contents Include
- Pre-MK3 and MK3 swingarm lubrication comparison
- Oil nipple, end cap and O-ring arrangement on earlier swingarms
- MK3 felt-wick lubrication system overview
- Welch plug and oil seal retention method
- Machining requirement for Pre-MK3 swingarm conversion
- MK3 bore specification of 1.261" diameter by .3" deep
- Photo comparison of Pre-MK3 and MK3 swingarm ends
- Need for MK3 bushings and matching spindle
- Old Britts upgrade kit reference
