B water coming out of radiator overflow

Do you have shutters on the radiator, or any other cover, and if so, are they open.
Running with excessive ignition timing will cause overheating.
Running lean will cause an overheat, richen the carb a bit, and check for vacuum leaks at the carb to manifold and manifold to head or a cracked manifold. Best way is to mist water around the connections and listen for the engine to drop RPM. Using ether por carb cleaner, etc., will work, but since the intake and exhaust manifold are one, it tensd to light off and burn up the machine. Gasket leaks are not unusual on these machines.

2)After running a while, shut down the engine and feel the top vs the bottom of the radiator, you should be able to tell the difference in heat

3)Undo your bottom hose and pour a gallon of water thru the fill neck and see if it rushes right out

4) pull the thermostat and do a quick check in a pan of hot water to see if it's working

5) Also with the radiator low on water, and with the cap off, do you see water movement, showing the waterpump is working?

6) with the cap off and engine running, do you see a lot of bubbles comming up? One of the signs of a leaking head gasket.

Just a few things you can try that don't cost money.....
Good Luck