If not already done, would assure correct ignition timing, and that the advancer is properly functioning.
Head torquing after head gasket replacement is done on a stone-cold engine. After torquing on the stone-cold engine, run/ride until engine attains normal operating temperature. Allow engine to get stone-cold (sitting overnight is best), and then -- without loosening anything -- torque again.
Just a general re-torque in an effort to reduce a leaking head gasket should be done on a stone-cold engine. I first try to torque each fastener in the factory prescribed tightening sequence without first backing anything off, which may result in zero movement as if already sufficiently tight. If so, then, as Nessism says, back off the nuts enough to get them moving before tightening them to specs.
I'm uncertain whether it's best to first slightly back off all the fasteners before the re-torque, or just back off and re-torque one at the time, or if it really matters. I think the most important thing is to have the engine stone-cold, and to tighten in the correct sequence.
Good Fortune!