By David Porter, Customer and Technical Support at The Bonneville Shop
One topic that comes up occasionally when discussing the early unit-construction Triumph B and C-range telescopic forks is the fork oil seal holders, or “dust excluder sleeve nuts”, as termed in the Triumph parts catalogs. The new external spring forks introduced on the 1964 models replaced the internal spring forks, as used on the late pre-unit and 1963 unit-construction models.
They were an improvement in many respects, with the sturdy 33.5mm fork tubes, chromed seal holders, and wide gaiters imparting a muscular look to the 1964 models. Despite the improvements to the new front end, there were still some updates needed to be performed at the dealership upon set-up of the motorcycles right out of the crate – such as eliminating oil leaks.
Triumph Service Bulletin 64/1, published January 17, 1964, details a couple of them, with a reference to “Blue Bulletin #4”, from November 8, 1963. The bulletin provides basic set-up instructions for the 1964 twin cylinder motorcycles, but a seemingly extra step is included, where the fork legs were to be removed, and the chrome fork seal sleeve nuts removed. The threads were to be cleaned, and a sealant applied to the threads prior to reassembly.
Another step was to fit a 57-1071 felt washer (later updated to an 82-4047 cork washer) between the fork spring abutment and lower fork lug, serving as a seal to obviate water contamination in the fork lower. The designers were using whatever they had on hand for this “seal’, as the felt washer was a transmission bearing seal, and the cork washer was the gasket under the oil tank filler cap. This procedure was suggested in the aforementioned Bulletin #4, with no mention yet of the fork seal sleeve nut sealing instructions.
“Although the 1963 models were the very first unit-construction Triumph 650 motorcycles, the 1964 models were still essentially a new and unrefined machine.”
There were many Service Bulletins to emerge during the 1964 model year, but this one is important as it illustrates the running updates performed as more feedback from the dealerships began to filter into the service and design departments at Meriden. Although the 1963 models were the very first unit-construction Triumph 650 motorcycles, the 1964 models were still essentially a new and unrefined machine. The many revisions to the 1964 and 1965 models resulted in a much more refined B-range of 12 volt motorcycles for the 1966 model year.
Going back to the original area of interest for me in this particular Service Bulletin, the 97-1654 fork seal holder sleeve nut was still specified for the Triumph twins through the 1966 model year and still required thread sealant if it was expected to be oil tight otherwise eliminating oil leaks might not happen.
Triumph finally updated the seal holder sleeve nut by machining a groove into the threads to accommodate an o-ring during the 1967 model year production, although the part number remained the same as the previous 1964-1966 iteration. The o-ring fitment commenced at number DU52096 and continued into the 1968 model year.
The use of sealant or Teflon plumber’s tape is usually adequate eliminating oil leaks and keeping oil from weeping out of the joint where the seal holder is threaded onto the fork lower. The Bonneville Shop offers the 97-1654 seal holder sleeve nut in the original non-grooved condition, in both chrome-plated and stainless steel. It is not clear if the 1967-1968 97-1654 grooved seal holders are being reproduced at this time. Further improvements to the 1968 models came in the form of the “shuttle valve” forks and the change to UNF threads on the fork stanchion tubes, cap nuts, and bearing nuts.
I hope you have found this bit of history informative and helpful.
