when you do the adjustments on each cylinders intake and exhaust rockers make sure its on tdc so both valves are fully closed (easiest way is to turn the engine till the opposite cylinders rockers rock between the exhaust closing and the intake opening then you know your on tdc for that cylinder ), check and set the gap then move to the next one.
the opposite cylinders are 1-6,5-2,3-4 i hope this is understandable , and helps you mate !
someone else may have an easier way to do it ,this is just the way ive done it for years .
cheers chris.