Vincent,
That looks like a rear brake plate being used on a front wheel

The requirement to update SORN annually was scrapped a long time ago. Once on SORN it stays that way until retaxed.

The danger of fitting a ball race in this position is that it then becomes the crankshaft endplay locator rather than the timing side bearing. How are you proposing to get round this potential problem?

New ones available from Draganfly

Rivet counting 'in extremis'. Depends on how often they have been renewed (if ever).

As the fibre rubbing strip is missing I wonder if a previous owner put that in to stop the spring tensioner from flattening out too much. Also intrigued by the four screws behind the magneto sprocket.

I do not know how thick that disc is but there is a fair chance that the sprocket will rub on it. I did not think that there was any need to do anything, there was enough metal remaining to stop the bearing outer race moving outwards which is all that flange does if you are fitting an inner seal.

The schemtic is available on Draganfly's site

Hi Alan,
Try <www.parallelengineering.co.uk>
They are based near Wolverhampton and specialise in very accurate frame alignment.

Tappet blocks are available from 'Morgo'. Draganfly are the only source I know for cam followers. Club spares may be able to help with second hand ones.
RR