Do they all have primer buttons? mine is a 675, can't find it.

Does it stay running after you squirt fuel in the carb opening? If yes, then there may be a pin hole leak in the hose going from the fuel tank to the primer bulb and it is adding air to your carb.
Thanks

clean the carburetor clean the fuel line filter adjust the idle screw on the carb as well

Check the pickup hose in the gas tank I would suggest replacing it.

Many Briggs engine have a primer rather than a choke, the 675 series has a choke that is worked by an air vain, the choke is always closed when the engine is stopped, once the engine starts air pressure from the flywheel pushes the air vain which in turn opens the choke to allow the engine to run normally, there is also a version with a bi thermal switch on the back of the muffler, as the muffler heats up the switch opens the choke.

either the passage is plugged or the bulb is torn

Your primer bulb has a pin hole in it. The part number is 5085H This is an aftermarket replacement for the original 694395 primer bulb.
Web image search:
http://www.google.com/search?q=Briggs%20and%20Stratton%206.75%20Hp%20Primer%20Bulb%205085H&rls=com.microsoft:en-ph&oe=UTF-8&startIndex=&startPage=1&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&hl=en&tab=wi

Another part number (original Part) is 694395
http://www.discountsawchain.com/servlet/the-401/Briggs-%26-Stratton-Primer/Detail

http://www.briggsandstratton.com/engines/shop/parts-and-accessories/?part=694395

Thanks for choosing FixYa,
Kelly

Sounds like the primer bulb dry rotted from sitting &/or the float is stuck in carb. If gas is indeed leaking from bulb. It will need to be replaced. While it is apart, clean carb inside & out with spray carb cleaner.

if you dont see a primer bulb then you must start it in choke mode after running out of fuel

don't waste time looking for the primer bulb. probably wont work anyway if its over 6 months old and repairs probably wont do any good either. bad design for a primer system.