BSA Owners' Club Workshop Discussions

The BSA Workshop => Singles => Topic started by: watts on 09 Aug, 2025, 23:16

Title: Plunger M21 Clutch reassembly
Post by: watts on 09 Aug, 2025, 23:16
Looking at the parts fiche there is a felt washer then a cork one before the driving sleeve. The first part to go on after the rear primary case. Part 11 and 12.
It appears to me that with them on the driving sleeve is loose, and only the key will stop it turning on the shaft, which seems wrong.

Or does tightening it all up squash it sufficiently to get a tight fit on the shaft.

When I removed it, it did not have a cork washer and it is a better fit?

Thank you
Matthew
Title: Re: Plunger M21 Clutch reassembly
Post by: neil1964 on 10 Aug, 2025, 16:10
Confess that when I've stripped these down (generic 6-spring clutch) I have never noticed the cork washer (or was it stuck with gasket goo to the cover) and the large felt washer is held in place by the oval slotted plate?
Yes, the Woodruff key and the taper are critical to holding the assembly on the mainshaft.  If you assemble it without the key and tap the hub onto the shaft lightly with a mallet you should get a nice snug fit which resists rotation.  However I did managed to shear a Woodruff key when applying most of an ABSAF 600 engines power through it.
Title: Re: Plunger M21 Clutch reassembly
Post by: watts on 11 Aug, 2025, 11:10
Hello

Thank you here is a couple of pics, with felt and cork washers. With nothing on the shaft nice snug fit but with both on not good, just felt is ok.

Thanks