I believe it's from the timing gear case. There is an old black and white film of the Triumph factory assembling the engines and one man was testing the gear tooth lash from a stack of gears before installation. This sound is common on pre units. I believe later 650 unit engines use timing gears that are wider and can be installed. I hope my 1951 6T like this one that I'm restoring doesnt make that noise because I wont rest until I eliminate it.
@@dubes5594 thanks tor that Dubes. I've had triumphs from 1971 and still get the feeling on my T160 that I did when as a kid who swept the floor at the local bike shop, got to ride a brand new T150 6 miles to get its first warrant of fitness or MOT.
