Copper 'age hardens'. I once worked as a storeman in a plumbing suppliers and the time-served old boys wouldn't take the older darkened copper tube as it wasn't easy to use/bend. They insisted upon having bright shiny tube.
Anneal (soften) the gasket by heating all of it to cherry red then either dropping it into cold water or leave it to cool naturally. It doesn't matter which but dropping a used gasket into water will shock off any sooty dirt.
I use my gas cooker. For some reason the flame and the gasket's cherry colour don't show in the photo......
The dish is full of water........
The whole gasket above is annealed. I took a second grip of the gasket in a different position and heated it but it shows darker by one bolt hole.
As far as the oil goes I would guess if the level dropped 3" ( ) in a couple of minutes it's likely to be a scavenging rather a burning issue but I cannot see why it would do that just by replacing the head gasket. Draining the sump will give you a good clue as to where it's gone.
I've never had or worked on a L/W so won't venture any further into the oiling issue
Edit:
Is it possible that the oiling fault was there or developing already?..... If the P.O. fitted a head gasket incorrectly......vigo wrote:Recently bought this bike it had lost compression. The headgasket had been in correctly fitted by previous owner.