Okay – so I’ve committed the mortal sin of posting my project progress a short time after I’ve actually done it. Consequently all the great ideas and advice I get make me feel a total idiot as I’ve invariably done the absolute opposite! So here is it right up to date.
Clearly I’m a lazy git, but when connecting the battery I found I was suffering from disintegrating loom syndrome, and every piece of wiring I touched fell to dust in my hands. This and that I didn’t know just how bad the condition of the motor was meant that instead of pulling the motor out and apart as would have been wise I took the easy route. I hung the whole bike from the roof the garage and pumped paraffin into the reed block aperture of the bad crankcase (right side), letting it spill out of where barrel was no longer into a tray before pumping it round again.

Tooth brushes, bottle brushes, pipe cleaners, anything I could to try and do what since the elf and others suggested of a total clean up (but without stripping the motor). Repeated the process for about 3 hours until I thought I’d done enough, but thinking about it I probably hadn’t.
Barrel cleaned up okay –plating looked good, but had some weird stains? Rings well and truly stuck in piston but removed, grooves cleaned, small end felt good, everything reassembled. Ring pegs a novelty to a 4 stroke guy.
Read block assy. stripped and cleaned
Carb in terrible state – cleaned up okay,

Power valve repaired!! (take a bow Glen from work) Actually better than before I broke is as grooves had been worn by the seal and know they’re gone! Thanks for generous offer though Corky. It is stright by the way, although the photo makes it look bent!

All back together with about 3 gallons of two stroke oil on assembly, premix in temporary tank and.........
You’ve guessed it , it burst into life. Fuel dribbling everywhere from float needles still suffering bits of dirt in them, and temporary fuel tank (can't even get the cap open on the original), but it runs all the same. Since then I’ve had the clutch out as all plates where stuck and that now functions fine. I’ve checked oil pump and that seems to be delivering as manual states. I’ve started de-seizing the brakes – the fronts aren’t actually too bad. Everything seems a little better than it did when the motor whouldn't turn!
But – unsurprisingly the motor sounds to me a little like it shouldn’t.
I suspect it’s mains, and if it was a four stoke I’d just ride it until it really broke and then repair it. Remember the challenge - just a few laps isn’t very long (under 20 miles). But it seems as though my barrels are good, and a couple of balls out of the mains being lobbed through the transfers isn’t going to make them any better so I really shouldn’t run it any more. I may need one of you guys to cast a trained ear over it. I live near Ipswich in Suffolk, anyone fancy a cuppa?, or I could pull it to yours on my trailer?
So I’m sure there will be more to come but my immediate need list if anyone can help is: slide for std 29mm carb (height adjusting nib had broken off one of mine – I found it in the reed valve - eek), rear disc (mines rizla thin in the middle), a tub of fibreglass resin the size of brazil and more time to work on it!