I still have a small spanner on my key ring that fits the mixture adjusting nut on the bottom of SU carbs.
Last needed it on my 1976 Triumph 2500S........along with the trusty colourtune.
I could only get it to run smoothly when the engine was running 'rich' which gave 13 MPG.
Still own a Carmine Red 1976 Triumph 2500S which I bought in 1998. Great car, and still rust free (I did a lot of rust preventative measures when I got it). I get about 24mpg on average - it runs sweet as a 'nut'! A bit less whilst towing, but as long as it is running well, the mpg is not worth worrying about! Get plenty of 👍 when out and about from other 'knowledgable' motorists...
My 1976 2500S was finished in a fetching shade of jasmine yellow and looked very smart with standard fit 'Stag wheels'.
Being a long stroke OHV unit designed by Brunel
it was not fond of high revs, but had good low speed torque with overdrive fitted on second, third and top.
It was about 6 years old when I first owned it. The tin worm had already eaten through the sills and the floor under the back seat.
PAS as standard which was not common on cars built in 1976.