I had my 400F apart last winter to put in 1st over pistons, and I put it back together with a brand of gasket kit I had never heard of before (D&K or something). Half way thru summer I started getting leaks from everywhere, base gasket, head gasket, valve cover. I pulled it apart again this winter and the rubber o-rings were hard as a rock and came apart in pieces.
I put it back together with a Vesrah kit, hoping it's better quality. Too bad you can't just buy a top end kit direct from Honda any more.