Normally, the filter element is retained to the bolt by a spire washer, which keeps the head engaged with the flats to stop it turning. You are missing parts from the air filter - on each side, there should be a rectangular section plastic tube, curving through 90 degrees, which is inserted though the hole in the element (which goes to the bottom), angled downwards, and passes through the opening in the air box, so that it picks up air from behind the engine. On my 78, they had made some improvements to the side panel fixings. The airbox cover is held on by a nut and special coil spring washer, which means you don't need to tighten it so much, but it doesn't have a retaining screw to hold the panel on - the back of the panels is moulded to hook round the frame tube, so you only need the springs at the front to retain it. I don't envy you, having to put right a bike you're not familiar with, when it has been bodged and butchered by any number of cowboys over the last 47 years. I was luck with mine, it hadn't been molested when I bought it 31 years ago, so everything was in the right place from the start. I'm sure your persistence will pay off.

Hello Angus. The Silver Jubilee has a threaded deep nut that holds the inner black air cover on and then a large chrome Pozi drive screw fixes through the outer cover for retention as well as the springs. Check your Siver Jubillee supplement parts manual for what your missing. Cheers!

It’s coming along nicely. It’s not a surprise that you will come across bits that are bent or missing fittings. I’m sure you will suss it out though.