Leaking Carburettor (on a mower)

[wattsie_2004]

I have been given the task of mowing a large lawn, alas it is rather a large lawn (40x40 yards by my guess) and the sit on mower that I was to use is leaking, nay, *pouring* petrol out somewhere around the carb.

Its a Briggs and Stratton sit on mower. The access to the engine is limited by various covers / parts of the chassis but is accessible with a bit of patience.

However I am not familiar with mowers and wonder whether anyone can offer any pointers - such as whether this is sort of gasket problem, or whether the carb is clogged up etc.

Hopefully theres a mower expert around somewhere
Cheers

P.S. I prefer to do what I can myself, so dont want to fork out on repair costs, sending it away, if I can help it.

[Pigeon]

Float valve not seating properly, strip and clean carb, make sure there is no st in the valve and that the needle is not jamming/hanging up.