I had a 1953 G3LS jampots, dualseat, from new.
After a couple of years, a tappet noise drove me mad.
It was not always there, & would come on quite loud.
The manual said, adjust the clearance to NIL, warm.
I tried every temp from slightly warm to very warm. no joy.
Eventualy i spotted that one of the cams was kicking sideways when lifting.
Must have had a slope. Shimming the end float cured the problem.
A quick story, in 1952 a hard up mate wanted to sell me his 1,000 black shadow for £100.00, could not aford it. :-(