Thanks guys for your quick responses.You guys are definately on the money, The "round thing"is definately a fuel pump of the daiphragm type pumped by crancase vacuum.You can see the line comming from the crancase in the first photo. I have very carefully pulled this apart to check for damage,and apart from being fairly basic in construction, it appears ok.When I pump the primer bulb there are air bubbles in both the bulb and the fuel filter after the fuel pump.If there was an air leak wouldn't that translate to a fuel leak at some point??
