This saga is over. After a bout of flu and the seasonal festivities I can now report that the XBR is up and running again and got its MOT last week. I took the barrel and piston to the local machine shop and confirmed that the the bore, piston and rings were well within tolerances. Anyhow I had the bore re-honed, fitted a new set of rings and tried again this time following Bill's advice by starting the bike, checking oil was getting to the camshaft and heading out for a good run before the clouds of smoke could develop. After stopping briefly to check for oil leaks and about forty miles of varied loads on varied roads all seems to be well. The treatment will be repeated tomorrow.
I really appreciate the help and advice given by all who took an interest. Can't say I will follow this running in procedure on my Velocette when the time comes but maybe with very close tolerances and modern oils it's horses for courses. Thanks again.
