"IN" does go on the carby side and the gasket is also marked with "IN" and an arrow. You say the noise is apparent with the covers nipped down, is this both covers?

the gasket might be getting squished out the way a bit?

I think its sorted, added a liberal coating of silicone gasket to the front cover and no more noise.

I think the gasket has aged and was letting the parts touch?

It is running sweet, for now..

Well bloody hell its started again once the engine has warmed up. It is pulling strong especially since I replaced the rubber mat in front of the carbs.

I know its something to do with the front rocker cover but am stumped.

Wild stab in the dark but could the head get starved of oil if the pick up is blocked or dislodged somehow?

Sounds like the old gaskets have compressed,
Take cover off,Remove old gasket, clean gasket and cover, when dry put a bead of silicone in the grove of the cover,
Place the gasket on cover, then turn cover over and place on a flat surface.Leave it for an hour or two then refit.

Drunkard, will look in to that.

Hunter, thats what I did previously, its odd it has not worked long term, I think a new gasket is in order, anyone have one?

Gasket ordered from Rick Oliver.