Rubber membrane for pump for Vire 12 (Bing)

this part was never designed for modern unleaded fuel, or salt air, so will in time (10 years?) slowly perish.

what will happen, is the rubber gets stiff or splits or distorts, leading to pieces of rubber jamming the carburettor jets, but more usually a loss of performance at high RPM. I have seen this on 50% Vire 12 engines having reported loss of power it is usually this part that is failing.

Its been very hard to source with great cost and delays, so i strongly suggest you carry a spare and change yours unless you know its been done every 4 years.

very reliable carburettor but this fuel pump membrane is the 'weak link' as its a rapidly moving part hidden from view and perishable.

pretty easy to change;

remove pump inlet, outlet, fixing screws, remove pump casing screws, tap apart to conserve gasket, clean debris, replace membrane. can be done in 5 minutes but in some corroded pumps you may need to use an impact driver on rusty screws with the pump held delicately carefully in a vice.

The actual whole pump is no longer made, but i have ones refurbished on request exchange.

there are basically only 3 problems ever go wrong with the V12 carb ; the float fails, the pump diagram rubber perishes, the choke solenoid tip perishes.(see other items). you cannot make any of those parts and will stop the engine performing/running, so carry spares.