Folks, recently picked up a good condition 508. Red knob on the on/off lever had melted at some point. Black control know was ok. Before firing up first time, fixed some obvious faults. Pump cup replaced, fuel cap seal replaced, generator fuel on/off nut tightened a fraction, and also the flame adjuster nut. On firing it up first time, 25 pumps, then 60 after light, it worked pretty good. So I let it run a while then shut it down. When cooled down, put it back into its nice silver plastic case. Came back next day to find fuel had somehow leaked out from somewhere and had pooled at bottom of case. Tank/fount was practically empty after being 3/4 filled. Dismantled completely, this time taking out the fuel/air tube and inspected schrader valve. Noted it wasn't screwed in tight. Anyways, removed fully, lubed with a little silicone grease and re-inserted and tightened up firm. Did not touch generator as this was working fine. Re-lit and working. Shut off and after cool down returned to case. Came back next day, no leaked fuel, Yes! However, there was no pressure in the tank/fount. On re-pressurising, came back next day, only to find that all pressure gone. I have another 508 and a 533 and both hold pressure for a considerable amount of time. Any pointers to where this leak could be?