Classic/Antique Car Repair: petrol leakage from float chamber, electric fuel pump, float chamber

Question
it has 2 su carbs
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Followup To

Question -
i have a 1975 midget with 1500cc engine,the car has been converted to electric fuel pump with inline filter,the right hand float chamber leaks through overflow/vent under certain driving conditions, i have replaced float,valve and seat but has made no difference as though pump pressure to great,any advice would be appreciated

Answer -
Hi Steve,
What do you mean by the "Right hand float chamber"? The 75 Midget 1500 only had one stromburg carb with one float chamber. Is this a 1500 or a 1275 Midget? Two SU carbs or one Stromburg?
Howard

Answer
It is probably a 1275cc engine then if you have two SUs.
It should have two hoses attached to the top of the float chamber, remove both hoses and remove the three screws holding the top onto the float chamber and remove the top of the chamber. First check the float level setting by turning the top to a 90 degree position form what it was mounted with the float hanging down. In this position the float arm will close the needle valve but not compress the spring loaded pin in the end of the needle valve. At this position you should be able to just slide a 1/8 inch flat plate between the float and the top. This is the correct setting. Now you need to pull the piviot pin that holds the float and float arm to the top. Be careful because now the needle valve can fall out. Remove the needle valve and inspect the point where it seats in the brass tube it is in. The point is about a 45 degree point and should not have a step or grove in the point. Now inspect the float itself, it should be light as it is empty and should not have any gas inside. A good way to tell is to shake it. If it has any gas in it you can tell when you shake it. Take a shop rag and soak all of the fuel out of the float chamber untill you can inspect the bottom. If there is brown or redish resadue in the bottom you probably should have the carbs cleaned.

Since you have replaced the float and needle and seat once you should not see trouble in this area if you set the float level correctly (1/8 inch)If you replaced the spring pined needle with a solid one piece needle that may also be the problem. If all this is correct you need to put a fuel pressure gauge in a "T" connection close to the carbs to see what the pressure is. It should be about 1 1/2 to 2 PSI. If you have a pump that is much higher than that you need to either add a regulator or get a different pump.
Howard