TOPIC:

On the left hand side of the tank there is a fuel supply tap which connects to the main supply tap on the right. What is the impact of keeping this closed? I assumed it simply a feed from the left side of the tank but I'm wondering if this is actually the reserve???.

So far as I know, that is just a feed from the left side of the tank. The right side tap has the on and reserve functions from wherever it gets fuel from. The left tap has a tendency to leak, due to the O-ring and the poor quality metal, which can corrode. On my #1 bike, I have the feeling that fuel flow into the empty carb is not very quick, so I usually switch the tap to reserve to get the motor started.
I've got to admit I haven't touched either of my complete Nordies for a long time, so I must haul them out!
Nick

Thank you for your response. I thought this to be the case. I was worried I'd given the new owner the wrong information. Hopefully he'll read this.

So you've decided a Nordie is not for you?

It justified a full restore or using all the time. I've got a special ( see www.triumphrat.net/threads/daytona-1075-r.951034/) that occupies my spare bike tinkering time so moved it on . Enjoyed doing it and grateful to forum members for their help