As far as routine maintenance goes, no one is ever in a mad hurry to check and adjust valve clearances. It’s as involved as mechanical tasks get, short of a top-end or engine rebuild. However, you ignore them at your peril. Incorrect valve clearances lead to lumpy running, poor starting and, in extreme cases, burnt-out valves.
Everyone knows someone whose valve clearances have been rigorously checked, but adjustment has never been required. The brand name ‘Honda’ usually figures in such tales. Far be it from us to doubt the veracity of these legends, but the fact is that valves can and do go out of adjustment and motorcycle brands and usage really don’t seem to have much bearing on matters. Top-end rattles may point to incorrect clearances, regardless of where you are in the maintenance schedule. Also, don’t assume that all is well because the top-end is quiet. In this circumstance the clearances could be closing up to the point where the valves are in danger of burning out.