Torque Setting: ‘57 Tiger T110 650 Engine.

I’ve fitted a tachometer drive nut to the exhaust cam pinion. However, I don’t know what the torque setting should be. When I put it on last night, I set it at 40 lb/ft (50 Nm). In addition, the small pinion to the right of this, attached to the dynamo, has a slotted bolt/screw; I can rotate this bolt easily by hand in either direction. I’m baffled by this. Surely this is not right?