berrypicker
.020 Over
could be a number of things clutch basket damper springs ,torsional damper spring weak,my bike similar age and model developed a rougness and clunking in the lower gears around 10000 miles it was the inner torsional damper bearing it had been fitted the wrong way around and wore out prematurely ,have your triumph tech remove the sump and check for schrapnel in the scavenge mesh screens ,it will at least give you an indication if said bearing is on its way out