This was a relatively simple task. The Mille GT has small-ish Dell’orto carbs (30mm), but mine were both filthy. Also, they were fitted with simple bell-mouths, which were holed, presumably through vibrating against other components. Lastly, only one carburettor had a choke; the choke cable was tucked under the fuel tank, rather than being connected to the handlebar mounted choke control. I stripped the carbs, cleaned the components in my ultrasonic cleaning tank and re-assembled, using Dell’orto gaskets and seals (which you can still buy). They came up nicely, and I bought new bell-mouths for them. . These Dell’Orto carbs can be fitted with carb-mounted levers to provide an effective choke so that the engine can be started, so I also fitted twin choke controls.
By the way, a tip for carburettor cleaning: the little inter-dental brushes that you can buy cheaply are perfect for cleaning out the various apertures, tubes and so on within the carburettor. They don’t last long if you get petrol on them, but if you use de-greasing fluid, they’re OK.
Here’s the LH carburettor. The bellmouth (needs a clean already) and choke lever are both visible.