Camshaft nut used on 1970-on Triumph 500, 650 and 750 models. Also used on 1968-on T150 and BSA A75. 3/4-20 TPI UNF left-hand threads.
The nut retains the camshaft pinion onto the camshaft.
It is threaded on anti-clockwise and must be tightened with the engine locked.
