GET INTO THE GROOVE
Brian Richardson from Perth, Western Australia, has a question about Triumph rocker spindle O-rings. He says: “In my 1951 parts book, the spindles don’t have them. They appear in my 1954 and ’58 parts books, but the spindle part numbers remain the same, which seems odd because surely the spindles for O-rings have a groove for them; my spindles don’t, so how are they fitted?” I think Triumph originally assumed that the interference-fit of the spindle in the alloy rocker box would be sufficient to retain the oil – but this proved incorrect, so O-rings were introduced and the spindles had grooves to accept them. Because these spindles and O-rings could be retro-fitted to earlier models – and the grooved spindles could still be used without rings – I guess the plain spindle was effectively superseded and there was no need to change the part number.
One of the problems that occurs is that tapping the spindles in and out of the alloy box wears the hole, so leaks become more common – I remember one motor where you could actually see the spindles moving when the engine was running! On some, if not all, Triumph spindles I’ve noticed that the O-ring end is actually a pressed-on cap, so nowadays I would probably machine the box hole back to round and make a larger diameter end, but back then it was easy to pick up better boxes at a jumble. I guess if Brian wants to fit O-rings to an earlier spindle, he’d need to turn his own groove.