Henning took the top off the motor to clean carbon out of the combustion chamber and he checks the cam timing which may change due to chain-stretch.
Copper head gaskets transfer heat between the head and cylinder better and distribute the cooling load between the head and cylinder finning. He anneals the gasket before he re-uses it, this softens the copper so it conforms to irregularities better. You get it just barely red and drop it edge-first into water, done.
He puts the top end back on and sets up a dial indicator to degree the cam in, then he is finished and puts her back in the frame.
Henning did a lot of top-level vintage racing a while back, beating everything with his cb450 Drixton-Hondas including all the G-50s and Manxes. At one point he was "detuned" by a bad get-off that rung his bell hard. After that you heard of him more as a tuner than a rider.