OK, so, petrol out the RH exhaust implies that something is wrong with the LH carb.
If the carb overflows due to the needle valve not shutting off properly, then the petrol should run out of the overflow tube, so I would check that the overflow tube is not blocked.

However, if the float is not floating, then it cannot shut the needle valve, so I would chuck the float in a tin of petrol and check that it floats.
While at it I would also set the float level to 13mm.
I would also use a cotton bud dipped in brasso to clean the sealing face of the needle valve (carb body) and inspect the rubber sealing face of the needle valve to make sure it is in good condition.

Possibly pull the fuel tap out of the tank and see if it has any "gunk" in it.
Maybe put an inline filter in the fuel line from tank to carby just in case getting the tank painted resulted in "gunk" getting into the tank, and hence petrol, causing the needle valves to jam open.
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[color=#808080][size=9]Yes,.. I too know how to waste Time and Money,...