Modern unleaded fuels using 5%, or more bio-ethanol and many other potentially harmful additives (to the fuel system, not the environment) play havoc with the carburettor internals!
Failure to drain the carburettor/s for the winter lay up allows the petrol to turn into varnish, clogging up the carburettor jets and coating the float and float chamber, sometimes to the point where it becomes so difficult to clear, replacement of all the various internals may give preferable results?
Other suggestions of carburettor parts you may require are listed below:
It is sometimes just easier to fit new internals. Add as many items as you wish to the same shopping cart, new fuel lines, diaphragms 1350717C01, circlips 1339440D20 and float chamber gasket 1325844B00 for example, and still only pay the same single fixed price shipping cost. Pleas be careful to double check the part-numbers you order are correct for your model?