Get comfy, this could be a long read...
Firstly, thanks for the guidance and input, made things a lot easier.:red:
Done very little to it as it's been mostly sat in the shed but I get a message that says 'It appears to have an electrical fault'. What has happened is a wire came loose and rubbed on the front axle 'till it caught and wound around the axle. That pulled another wire and so on untill most of the loom was wrapped lovingly around the axle! Funny thing was that as it's a ground switch cutout and all the wiring was no longer attached in the correct manner, the engine wouldn't shut off until the petrol pipe was removed.
Anyhow, as a full rewire was just one of several things needed and it's not going anywhere anytime soon I thought I'd start with the gearbox. I took the bulkhead out (yes riveted in, but done by someone who got a riveter for christmas!) and could then see the gearbox mounting bolts which were very loose so that's now fixed. Also clocked the tensioner bolt so I now know where it is when I need it.
The rewire gave me the opportunity to remake, reroute and secure all the wiring and dispose of the much altered and modified (twisted, crimped, and scotchlocked) mess of copper that it came with. This one also has an aftermarket electric fan to draw air into the engine bay. Once I got it going it was rubbing on it's cowling so after about an hour of mucking around I put a bit of extra clearance in it. The fan is still under the bonnet and the cowling is in the scrap!
Next it's onto the 7 wheel drive. Right 1 is freewheeling. Made a couple of pins from some hardened steel haybob tines and beat them in. Then found the pin that locks the hub to the sprocket on R3 is missing. Found it in the greasy gloop under the drive chain and hammered it back in - problem solved. No, not quite. a couple of laps of the field and the pin is nearly out again so it now has a jubillee clip round the axle so as to cover the pin ends and keep it in place. Question is - the parts book seems to suggest these are supposed to be rollpins but none of the hubs on this one has them. They are all solid pins and appear to be 'interfearence fit'. How are they supposed to stay in place?