I have had problems with the fuel filter, the engine had a cough and the filter was very clogged.
You have to check it often and perhaps a slightly older one wouldn't be bad.
The other problem I had, almost when I new the machine, was the carburetor fuel solenoid valve. It started out failing from time to time until in the end it didn't work anymore.
Remove the cable and needle from this valve, and... the problem is over.
I don't think the carburetors overflow.
Another problem was the front wheels, ... very delicate. I ended up putting some bushes,... perfect
My translation is from Google, sorry for the language kicks...