Thanks Vando for the routine of starting, this is how I do it. (Except I don't kick it past TDC, I feel like I get better momentum from kicking it from the lockup point).

Using this mine is still taking about 20 kicks to start. Up to now I have now done the following.
1. Set the valve clearences (I got a special set of cranked feeler gauges for this).
2. Set the pilot screw. Screwed out just to the point of reducing the tickover and reversed about 1/8 turn. This is about 3 turns out. I didn't use PTFE tape on the screw - apparently it turns to snot in petrol vapour. Loctite thread sealant did the job.
3. Metered out the coil and cap resistances. All in specification.
4. Left the decompressor cable at 5mm clearence. Until it starts right I would rather have too much clearence than too little.
5. Fitted an iridium spark plug. No diffrerence to starting but a huge improvement in idling stability - would recommend this £10 upgrade to anyone with a single cylinder CDI bike.

Jobs tomorrow...
1. Fit new coil (£18 incl post from Fleabay). Despite the good resistances, I still don't trust the old one
2. Fit new float needle kit and seal the float bowl (the o-ring around the float bowl seal is a bit rough).
3. Hope it starts properly now.

The only thing I have left is the suspicion of piston slap and reduced compression (although it still locks well at TDC on kicking it over).. If it is that, it goes on ebay. I haven't the energy or the money to get it rebored.

With the proceeds I will buy an XT600E and be done with a right leg that Popeye would be proud of...

As always, I will keep you posted.

Jim