A very big thank you to all of you guys you made me think about the problem and earlier today I managed to dismantle and change the bullwheel! I'm so relieved! Yes you were absolutely right Charles and I followed your suggestion and although it was quite tight it finally came off the spindle - I used a rubber mallet. The putting together again was a lesson in patience everything was 'tight as' (kiwi expression) - the collar did not want to go back on again and although I gave it a good thump there appears to be a little play in the pulley cone - like it has not gone back on far enough. The ball race and adjuster went back ok and the end cog. I remounted the whole assembly onto the shell bearings after coating everything in oil and married up the upper bearing halves and shims. After everything was tightened down I ran the lathe with a mike placed on the front of the mandrel - it moves/flickers a fraction of a thou but looks good - no noise or vibration - no movement apparent from the pulley cone even with that slight play I mentioned earlier. So I'm hoping that might be problem solved - thanks once more.
Norman I hope your home damage is not too great - where abouts are you?
Hope the weather improves for you although in UK you are in winter now eh?
Mind you the summer here in NZ has been very disappointing so far. What takes you to Rotorua?