Rev Counter Drive.
I do not have a photograph of the inside of the timing chest cover.
The cover was drilled through. taped to match the thread on the Brass fitting shown in the photograph. This was screwed in, with some sealant around it and locks in place by the nut outside. It has never leaked oil
The part that of turns the inner drive cable, is a snug fit inside the Brass unit, formed square at one end to take the cable the other end is milled into a flat spade, that fits into the slot in the end of the camshaft drive and there's a tiny circlip that prevents, the inner part from falling out through the front.
By carefully measuring how far the Brass unit is screwed in, this secures the inner part with a little free play to turn, but not to rub on the drive nut, the ratio is a 2-1 anti clockwise.
The rev counter I had in those days, I think was out of a MG car, it was about the size of a Vincent speedometer, 5 inches diameter mounted on the handlebar, so the drive cable was only about two 2ft 6 ins long.
It was on there for at least 10 years, when I sold the bike in 85, but not when I bought it back in 2009.
In that time the Norton front wheel had been sold, because it would not stop!! With the BMW wheel, and the rev counter was also gone.
In that 24 years' absence, it and sat in a museum in the motorcycle shop in St Albans, Clarks in London Rd. When Tony Clark ceased trading he took the bike with him and a number of others, include a Velo Thruxton, DBD 34 BSA, a Rudge Multi and 1907 Premier
during it's holiday with Tony, the engine was never fired, or run, or ridden. When I got it back, in 2009 turned the engine over a bit, push up and down the drive without the spark plug in, it started third kick.
after about 5 minutes, there was a cry of anguish, scream! coming from the gearbox. so I did not run anymore. Took the gearbox off, and decided the dogs were dry. tipped the gearbox upside down or different ways, to get some oil around in it put it back on, started again no trouble, road up and down the road ( illegally ) and then decided to do a complete restoration, that took approximately five years, has been ongoing for the last couple, can I think I've really done it cracked now.
I'm sure Graham, you can sort out a way to make a little drive along the lines I said.
I've tried to find something on google, a photograph of the drive, a but nothing unless I troll through pages of triumph exploded engine diagrams