Mine pipe gasket was leaking, because the exhaust was slightly out of tolerance and had to be forced up to get the fixing bolt in.
Fixing that seriously quieted the motor.
There was also a loose clamp on one of the breather? emission hoses which was squawking.
Pro mechanics don't use feller gauges, they know the thread on the adjuster is 1mm/40 thou and have a valve adjusting tool with one thou clicks on the knob.
On my airheads it is possible to run the motor with the rocker covers off, and you can check the clearances by feel - shows up problems like rocker bearing wear or end float,
etc.
And any pilot error - DAHIK!
Surprising little difference between hot and cold, not much more than one thou, if anyone wondered!
Lining the bottom of the tank with some form of matt or heat shield works too - I had a bit heat shield, thin foil faced self adhesive foam and that has made a difference.
Stuck it everywhere I could when I was changing the shock too, made a difference.