The thickness of the sealing felt can also have an effect...Some pattern felts are too thick. When the nut at the rear is fully tightened the shoulder on the bolt sits against the rear face of the chain case.. The shoulder must be of a length whereby the plate and the felt are compressed to make the seal but are not so tightly held that they will not slide readily when the gearbox is moved to adjust primary chain tension...
I generally assemble everything and test the condition outlined above..If the bolts are too short you can fit shim washers under them to give more length...If they are too long you can try a washer under the head to take up the clearance...As I have a lathe I generally make mine to suit each time I build a bike, once I've worked out what's needed...
On my Gold Star I replaced the felt seal with a neoprene ring which I greased on assembly and that works well and gives a more consistent thickness across its surface and good support for the sliding plate....Ian
Thanks all
Ron
I looked at that bolt/screw it looks like the long ones I got myself
The shorter version is noticeably shorter
I’ll compare them tomorrow as in the U.K. again & in the sheds packing next 2 days
Br
Jo’b