Where can I get a primary chain tensioner screw 'Cap' from for my A65
Plenty or little rubber top hat grommets on ebay
The cap nut is 68-0377, should be plenty about, just google "BSA 68-0377". Stainless are about £7 but I'd go for zinc plated (about £4) as its less reactive with ally.
Thanks. found them on Fecked.
Quote from: limeyrob on 11 Jan, 2026, 11:51 The cap nut is 68-0377, should be plenty about, just google "BSA 68-0377". Stainless are about £7 but I'd go for zinc plated (about £4) as its less reactive with ally.
I don't understand why vendors sell this part as BSA modified it for 72 so that the hex is on the bottom rather than the top. (part no. 57-4424). The hex on an OIF A65 is more difficult to get to with 68-0377 fitted.
I bought mine from Burton Bike Bits, but it seems that the older type is only available from most places.
Yes I should have asked if it was OIF, but took the view that all A65 were Unified threads so it would fit. I had an OIF A65 and ran it for many years, I do seem to recall this cap nut was rather irritating, if the thread wasn't very clean the inner stud would turn as you did it up.
Hi,
Both of my pre OIF A65 have a lock nut that goes on the adjuster stud to keep it in the correct place. 68-0237 for all models.
I would suggest that the cap nut is there to protect the protruding adjuster thread and to perhaps even make it more aesthetically pleasing.
Dave.
Makes sense, perhaps my memory is fading! I bought the bike '72. ::)
my engine is 1967 so not OIF. Does this mean I've ordered the wrong part ?
It should be correct.
BSA Primary Chain Tensioner Adjuster Screw Cap Nut - BSA A50 and A65 Models Circa 1964-72
CODE: clutch0377-B23
Yes it should be correct, I assumed your bike was not OIF but should have asked before giving you the number.
I always put fibre or dowty washers in the joints between the cap nut and the locknut and the locknut and the chaincase. The Chaincase oil finds its way down the adjuster thread and weeps out if not sealed.
Hi,
I use sealing washers there as well. Over time the adjuster and case thread wears and oils seeps through. In use the action of the chain slipper possibly causes a slight rocking motion or it could just be the force pushing down when the throttle is shut off and/or when using engine braking.
I remember reading something about this being a weakness when the bikes were used for off road type competition. On landing after a jump the back wheel would bite and put huge pressure on the case as the bottom run off the chain took all the strain. The result was that the adjuster would push down through the case.
Dave.