When fitting the later 4 spring clutch things change a bit
With the single spring clutch the first cork washer/sleeve (37) that sits against the sprocket sleeve and inside the shaft adaptor
is not used when fitting the 4 spring clutch
On the six spring a smaller cork seal is placed between the clutch adaptor and the sprocket sleeve to provide a rudimentary seal (29)
I cannot see any cork seal being fitted in the relevant 4 spring clutchparts book. ??
You can look theough the BSA books online herehttps://www.baxtercycle.com/parts/parts-books-online/bsa/
I do not know if the M gearbox sprocket nut is the same as the A and B series ? on those you can buy a nut with inbuilt oil seal from SRM and others
Pattern sliding plates are readily available but they have two issues at least,
1, the centre hole is not an accurate fit onto the scroll on the back of the shaft adaptor
2, the two parts are rivited together and oil leaks out between the two, a run of sealant around the V gap should seal this..
The large felt disc fits between the primary case and inner primary clamped in place by the sliding plate
Special shouldered bolts hold the sliding plate in place but allow it to move when the gearbox moves for primary chain adjustment
Some people fit an other felt washer between the shaft adaptor shoulder and the sliding plate to help the scroll work ???
You will more than likely have primary chain misalignment after fitting the 4 spring clutch!!
You will probably have to space out the cush drive assembly to compensate and this can make fitting its nut a problem
The nut needs to be fully tightened to 65ft/lbs no matter what