Magnet on a bit of old accelerator cable/choke cabledown down the fuel filler cap works a treat.
But when it comes to replacing it.
Mind you, I always install a filter on the pick up pipe to stop the crap in the bottom of the tank reaching the fuel pump - a paint filter sold for use on the pickup tube on a paint spray gun is idea as it is petrol/solvent proof.
To do this you will need to remove the fuel gauge sender
Arwyn
