Modern unleaded fuels play havoc with any fuel system! Fail to drain the carburettors for the winter lay up allows the petrol to turn into varnish, clogging up the carburettor jets and coating the internals, sometimes to the point where it becomes so difficult to clear, a thorough overhaul using all new parts could be the solution, along with sonic cleaning or at the very least treatment in a good parts washer.
Below are other parts you may think worth renewing, but please check with our online schematic to ensure you order the correct number of parts: