both carbs ( Mark 1 Amals ) were really hot. I couldn't touch them for very long at all, so not just warm. It was really hard to start after I stopped for a quick check all was well after a few miles, could the hot carbs have anything to do with that?
Absolutely. Petrol engines work because liquid turns into vapour to mix with air. Liquid petrol vaporises at a very low ambient temperature (-43 Centigrade?) so, the higher the ambient above that, the faster it vaporises. Something like a carburettor is specifically designed to mix petrol vapour and air in the correct ratio for efficient combustion. By definition, the volume of air inside a carburettor is limited; if the ratio of petrol vapour to air is too high, the mixture won't ignite. A hot engine requires a weaker petrol-air ratio than a cold engine; a hot carb. will rapidly vaporise too much petrol for the available air, enrichening the petrol-air mix to where it won't ignite.
I've only used thin gaskets between the manifolds and the engine,
The parts book illustrations are crap
but they do show more than that ...
. (Thin?) Gasket 71-3573 should go between each mainfold and the head.
. If you enter "triumph 71-2813" (the part number of the carb. 'n' manifold mounting studs) into your preferred internet search engine, the returned images should show they're quite different from the parts book drawing ... Primarily, they're 'stepped' - most is 5/16" OD but the thread at one end is 1/4"
. Each carb. 'n' manifold fit over the 5/16" OD parts of two studs (I trust it's obvious they fit either side of the thin larger-OD ring on each stud?).
. Also between each carb. 'n' manifold is the thick O-ring 70-9711 on the parts book "Carburettor T140V" pages
. Finally, each carb. is secured on the studs by two of "Cup", "Insulating ring" and 1/4"
UNF Nut shown in the parts book on the manifold pages. The idea is each Nut can be tightened against the 'step' on the stud, which should compress the O-ring between carb. 'n' manifold but they should not touch, the compressed O-ring should form an air-tight seal. Because carb. 'n' manifold don't touch, engine heat can't heat the carb. (at least not by conduction) and there is some vibe insulation of the carb.