Like Steve UK and Blackrider have said, if the noise only lasts for a few seconds on a cold start up then that is fairly normal as the tappets pump up with oil. Are you running the correct 0W40 oil? The valve gear is a actually pretty robust with proper roller rockers, with the tappets just taking up the slack between the rocker and valve stem. They are pretty loose and rattly after the oil has drained out of them, hence the noise from cold.