Thanks Harco & CrisB
Harco
Vacume can not be a problem - steel line from carby to dizzy - and no, I did not touch the carby.
CrisB
I will try your suggestion and reinstall the dizzy EXACTLY as per book, (as this has worked for your hot starting problem).
I can see how valve timing can be out if teeth are misaligned, however if the dizzy is out by one tooth can this not be compensated for by rotation of the dizzy when tuning, ie. you are moving the body in relation to the dizzy cap hence obtaining correct firing.
Andy