julian Lindley

One final point, It seems likely that oxidation of the aluminium that the petrol tap is made from is contributing to the problem. Our machines are not young, and the taps have been immersed for a good while. My suggestion is to replace the tap also as its design is sealed. The large filter over also degrades and becomes brittle and fragile. Good luck from the UK!

This conversation, particularly Fish’s was an eye opener to me. What I believe occurs is that petrol is left in the fuel tank for long periods without being renewed. The chemistry of fuel has changed considerably in recent years with bio - ethanol being added and sulphur removed. Fuel degrades more quickly too. I I have noticed the tiny particles in the tank fuel cock and in the carb’s float chamber, they can stick to the Viton coated carb’ needle valve and cause overflow of its float chamber. It is hard to believe that the float settings would change, or indeed that the needle seat would be damaged. The fuel tank is frustrating to clean out as it is difficult to flush from its filling point. I spent a half day doing it using a funnel with a removable fine mesh filter into a large bucket, reusing the fuel after passing it through the funnel filter back into the tank and cleaning the filter each time in the process. A large amount of granular material in the petrol on/off cock demanded I replace it, particularly as it did not entirely seal, dripping every 5 seconds when the valve was turned to off, whatever the fuel head. I imagine that it would eventually equalise in pressure with the head of fuel in the fuel tank - more load on the float needle. So in conclusion I believe Fish is correct. Clean all of the components or replace and all should be well. I decided to purchase an OEM carburettor aswell.