The inner section of the starter clutch was then free to be removed from the crankshaft.
As expected the rubber oil seal was brittle and broken so I have ordered another one, along with a new starter motor chain. That job should be finished in around a week's time when the parts arrive.
With the starter clutch cleaned and the new springs fitted the whole assembly now works as it should.
They really make the bike look a lot better. While the tank was removed I fitted new spark plugs and caps, and I cleaned the air filter at the same time. The bike is now up for sale so please look in my For Sale section for details.