Yamaha t80 townmate carb keeps overflowing with petrol

carb flooding ! clean it !

Set carb float heights to standard
Possible crack in brass overflow tube

Sounds like fuel is overflowing from the carb , hence the fuel will also overflow internaly into the engine causing it to overfuel flooding the engine and soaking the plug in petrol, clean the plug, with the fuel turned off open the throttle wide while you attempt to start the engine, the extra air from the open throttle should be all it takes

They always were a beast to start.
make certain the carb is clean, if it doesent flood out the overflow they are usually OK
A nice clean and relatively new air filter can help.
the float needle can wear, so you may be able to drop the float level a bit ( often over the years people used to think raise float, more petrol,go fast)
they used to have two plugs in the head, B7ES, to start and warm up, then when its warm change to the B8ES.
sometimes the oil\fuel would settle in the the bottom of the engine, and as soon as it fires it picks this up and fouls the plug,
It can help to turn the fuel off and run it until the carb is empty, before it goes in the shed, and when you start it , turn the fuel on for 10 seconds then turn it of again and try to start it

The float is stuck open. This causes the overflow and floods the engine.

Your float is stuck and allowing fuel to overflow. If the float, floats it checks off the fuel exactly like the tank on your toilet.

You will have to adjust the float pin of tht particular carb and don't remove them off the rack..just pull them out of the engine and work on the one tht needs attention.
Hope this helps!

It could be the float, and or needle valve are stuck, causung the carb to flood continusily.
Pop the float bowl off and see what state things are in.

Hope this is of some help.
Ed

Float and or float valve stuck, flooding Carb. If it just can out of storage, it will need to have the carb cleaned.