I noticed that as well Norm. My Sunbeam (1972 I believe) ran smooth, but knocked on start up and spin down. Worn gudgeon pin/piston. Due to the fact it is so solid, I am planning on giving it a hone and new piston.
Don't usually do new pistons and all that, but the handles and alloy chassis are so strong (weighs a ton compared to the tin steel used now) that its worth it.
