Small Engines (Lawn Mowers, etc.): Lawnmower, engine model type, briggs stratton

Question
I have an old lawnmower a Briggs&Stratton 4hp at 3600 rpm 187cc. The motor was running smoothly until it cuts out one day and after that i battle to let it start. when i try to start it then it wants to go but then just cuts out again. It got spark and when i pulled the plug out then it is wet. Sometimes it go for 30 sec or less.

Answer
How old is the engine?  Often times, when a mower starts but then dies, is caused by a dirty carburetor.  When was the last time the carburetor was cleaned?

Please send me the engine model, type and code number so I can look up your carburetor.

Thanks.
Eric