You didn't say what engine model or carburetor you have, but you can go to http://outdoorpowerinfo.com/repairs/ and see if any of the pictures there look like yours.
with a big freagin hammer
Try this site: http://outdoorpowerinfo.com/repairs/
were can i find a wiring diagram for a 18 hp briggs and stratton engine
The intake valve(s) are not fully closing.
rotory carb
you can goto briggsandstratton.com and get a manual for that engine,
18 ounces
30/1000's
Go to http://outdoorpowerinfo.com/engine_specs/briggs_valve_gaps.asp for a listing of Briggs valve clearances. You'll need your model number which will be on the engine shroud or rocker cover.
The most popular place I know of for instruction is the YouTube site at the link below.
The fuel float may be stuck in the closed position. Or, the carburetor needle valve may be closed.
Raymond Briggs was born on January 18, 1934.