You may recall I had a meltdown in my 1963 r69s. Both pistons melted, left worse than right.
So, I have cleaned out the melted piston bits from the head, scraped off the melted piston from the valves (bench grinder was great for that- they just flaked off). Cleaned off the melted piston from the ouside of the valve guides (dremel tool with brass wire bush). Valves lapped, held gasoline in the chambers with no weeping, so I went to start to get the bike ready for the new pistons and bored cans.
I went to clean the engine case, and pull off the old gasket. Here's a pic. There was so much sealant that it plugged the oil passages! Check out the top of the gasket- you can see the sealant oozed into the space and blocked it off. The bottom holes were likewise plugged. While I'm not happy with how this played out, at least this was not my handiwork!