New Holland Boomer 8N Carburetor is overfilling

[berryjuice_]

I'm trying to help a buddy out with a major headache on his New Holland Boomer 8N tractor. He's pulling his hair out because whenever he opens the fuel line to the carburetor, it immediately overfills and starts spilling gas everywhere.

He's already checked all the obvious stuff, the floats are good, the plunger and seat are clean, and the orifice is clear.

He's a decent mechanic, and he's completely stumped as to why it won't stop leaking.
The fact that none of the usual fixes are working just doesn't make sense to him. Any ideas on what else could be causing this? We're at a total loss here!

 

[RottenTomato1]

A good looking float doesn't mean it's not the float, it just means there could be a problem you're not seeing. I've had something similar happen to me a couple of years ago and it turned out that the float needed adjusting because it wasn't lifting enough to create a complete seal.

 

[Fenza mike]

Apart from the carbs, look at fuel pressure too an plus what @RottenTomato1 has said