Hardyboater,
which type of gasket did you use, the 'old style' rubber ones or the newer type which snap if bent?
It doesn't always hold true, but in this case the older type are better...
Maybe worth checking that there's no damage on the mating surface of the cylinder head.
p.s. Don't forget to glue the gaskets onto the covers with Evostik or similar, then use only a light coating of oil or grease on the face which contacts the cylinder head.
One of my pet hates is finding a gasket which has had gasket goo plastered onto both sides, almost as bad as those which are chucked in loose.
Note that the gaskets should not need changing every time the rocker covers are removed.
This suggestion seems to originate from the same sources which advocate changing spark plugs and leads about every 3,000 miles.
Tom,
I'd agree that over-tightening can cause problems, but so can under-tightening.
About 2 turns from finger tight will be closer to the mark, going on this test...
ken
1 turn of the nut gives 2.6 Nm, 0.25 kgf m by slcchassis, on Flickr
2 turns of the nut gives 5.0 Nm., 0.5 kgf m. by slcchassis, on Flickr