Hi, need more details really(engine size/type, symptoms etc) so i'll have to guess that the bike stops after a while? If the petrol tap is of the vacuum type, when the petrol feed pipe is disconnected there wont be a flow of fuel, there should be another similar pipe connected to the back of the petrol tap the other end should connect somewhere forwards of the carb or onto the inlet stub this pipe has a vacuum in it when the engine starts which then pulls open a rubber diaphragm in the petrol tap thus letting fuel through. Another problem could be a blockage in the feed pipe or petrol tank cap breather hole, both would stop fuel reaching the engine.
Chris P.Duck, February 2011
