1750 won't start

A mate of mine drives a 1750 junior.Problem is,after he has driven it for a while it won't start again untill the engine has cooled down.I suspect,coil,I could be wrong.Any ideas?

Might be fuel evaporation too.
It's a bit difficult to say really you would need to start checking everything bit by bit to rule things out.
Is there a spark?
Is fuel coming through?
Are the plugs wet?
Does it fire but not pick up
etc etc

Thank you for the advice.When I looked at the carbs,they seem to be flooded,air cleaner box have a lot of fuel in it.