Hi mossy, This is interesting, I had the same problem about 25 years ago and the fault was in the vertical drive gear to the distributer, for some reson there are gears that fit ok but give the wrong drive ratio to the points. Set the ignition timing and then give the engine another turn and check it again. If you have the wrong gearing,although you have just set it on the next revolution it will be out. You also mention the distributor clamp, and this can cause problems because if it,s not holding correctly will of course alter the timing. Another problem was after market points, where the flat plate spring had been made from spring steel that was too strong, so instead of just sliding round the lobe it was gripping the lobe and moving the timing weights, make sure it rests on the lobe but not over forced.
There is a choke slot on the original carburettor but no choke was fitted.
One last thing when you are trying to start after a few kicks take out the plug to see if it,s wet. Obviously if it,s dry there,s no fuel getting through.
