I've now logged 200 miles on my newly rebuild '53 Square 4 MK II, and it is all coming together.
One worrisome issue, however, is I've been noticing that after a good ride, with the engine heated up, if I put the bike on its side stand, I see petrol dripping from the carb. I can right the bike to level, and the leakage quits. Along with that, at all times, even if there is no leakage, I have observed that with the bike on its side stand, the idle speed decreases noticeably.
As near as I can determine from looking at parts explosions, inexplicably there seems to be no gasket between the fuel bowl and the carburetor.
I have completely disassembled the carb and run it through my hydrosonic cleaner, and insured all the jets are free. I see no evidence that the float has sprung a leak.. I've never heard any liquid inside when the float is out.
Some have suggested a shim washer underneath the needle valve, but I don't see any reference to that in the parts listing either.
Soliciting any opinions and suggestions.