Hey there,
I believe that this hose could be the vacuum that connects from the carburettor to the petrol tank valve/pump. Normally these engines have a vacuum operated petrol pump that is taken from the carburettor or sometimes the 'inlet manifold' and connects directly to this pump.
If however your petrol is leaking out this could mean that the petrol inlet to the carburettor has become detached either from the pump or the carburettor itself.
Post a photo of the carburettor showing the hose and also a photo of the petrol pump and I could help you further.
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