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For Triumph and BSA forks up to 1970 (up to 1974 on the Triumph 500 twins and some of the BSA singles) a fork damper sleeve is fitted between the bronze fork bushes on the stanchions / tubes. The damper sleeves may be aluminum or plastic and they serve 2 purposes:
- Keep the fork bushes from bashing against each other when the forks are pushed to their limits.
- Act as a metering device for how the fork oil moves inside the forks, thus dampening the forks.
The damper sleeves themselves are not anything fancy. They are, quite literally a sleeve with a uniform outside diameter that fits snug inside the fork lowers. close examination however you will notice that the sleeves have 2 different inside diameters.
A question we often get asked is, “Which end of the fork damper sleeve faces up, which end faces down?”
The smaller ID faces downward, the larger ID faces upward.
The smaller ID blocks the oil passages on the fork stanchions and blocks the lower holes entirely when the forks top out, thus trapping oil in the stanchion and restricting movement so that the forks don’t overextend and slam the bushes into the sleeves damaging the sleeves.
My experience has been that the assembled fork oil seal holder, complete with the fitted oil seal, thin steel washer, upper shouldered fork bush, and O-ring, is slid up the fork stanchion tube from the bottom. A light smear of fork oil on the stanchion will help the assembly move upwards easily.
Next, the fork damper sleeve can also be slid upwards on the stanchion, with the inner lip facing downwards. The lower fork bush can then be pressed over the reduced diameter receiver on the bottom of the stanchion. Sometimes a light tap with a mallet will assist installation of the bush. On the post-1967 forks, fit the shuttle valve into the lower bearing nut, and secure it with the circlip.
Once the lower nut is tightened, the entire fork stanchion is ready for installation into the lower fork leg. The stanchion assembly is offered to the lower leg with a coating of oil and the sleeve nut (oil seal holder) can be threaded onto the fork lower and once tightly secured, the assembly is complete.
A good way to determine if the sleeves are installed correctly is to put the bike onto its main stand and listen for a CRACK from the front end… if fork damper sleeves are installed upside down, they will not block the lower holes and thus will allow the sleeve and bush to make contact. You will want to rectify this situation and switch the sleeves.
Check our tech article and video on front end tools to help get your forks up and running. In it, Stacy goes over the many fork tools that we carry including the 1.5 inch fork top nut spanner, the billet fork nut wrench, the fork seal holder service tool wrench, and lower fork spanner. Whatever the job you’re undertaking on your classic Brit bike, we have a host of tools, parts and articles to help you along the way.