won't start TR4

[Sebastian_King@ipc.co.uk]

Why does my TR4A keep failing to start? - eg, been on a drive, park car,
comeback - turns over but will not fire. 

I've noticed that when this happens in-line filter is empty and I need to
disconnect the pipe from the carbs, turn the engine over until the petrol comes
through and reconnect.

It'll then start - why is this happening?

Seb