Thanks for the offer. As I said, I'm no mechanical genius so any help is appreciated. Not trying to be a smart alec but I don't agree with you on the non return valve thing. I reckon the pump would work whether or not the valve was working. The difference might be that the fuel may want to head back down into the tank rather than maintain some sort of pressure to the carby. I've had both of mine apart and one is now good after much cleaning and the other just will not work. Perhaps the ball is too rusted.
Like I said - not trying to be smart - just my opinion.
