[Darren69]

All the comments and deductions seem logical to me and would suggest that the vacuum pump is the cause. The only carb Ducs I've had before have been SS's which have an electric pump in the tank and I never had any issues with any of those. But to re-iterate battery, battery, battery! It has to be in top nick to start one especially if its been laid up for a while and dried out so regular start ups will help too.