If fuel is spraying out the TOP of the airhorn, I would agree with Stuart that possibly one or more of the intake valves are not seating. This would cause a pressure in the intake manifold instead of a vacuum, thus blowing the fuel out the top.

A compression test will prove or disprove this diagnosis.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
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