You have a very desirable bike there, do you have any details on who did the rebuild, it can make a huge difference to what is going on inside, if the bike has stood idle since the rebuild, and the rebuild was done properly you should not have touch the valve clearances to get it going, but it would be advisable to follow certain procedures for pre-oiling the engine before attempting to start it, there could be a few dry surfaces in there that would definitely benefit from being well oiled before starting it.