The OD of the carbs is 46mm, ID = 40mm. I'll probably make the manifold using 48mm tube (nearest I can get without reducing ID to below the carb size).

What sort of connecting pipe is available? Or do most people just use the pipes off the bike?

I guess standard silicone is a no-no with fuel.

bttt

You cant use standard silcone hose you need the correct fuel resistant lining
contact samco as i am sure they will sell by the metre
or chester sportscars sell the pipes to connect to a bog bros manifold for zx6r carbs for a fiver each !!!