Look for a MODEL & TYPE number on the engine.
That will allow us to determine exactly which engine it is.

http://www.outdoordistributors.com/Briggs_And_Stratton/briggsmodelid.html

Since it ran well for so long, the first thing I would check is the fuel bowl on the bottom of the carb for water. You'll need a 1/2" socket. With the engine cold, pinch the fuel line from the tank or, better yet, remove all the fuel from the tank. Loosen the bolt from the bottom of the carb and let the fuel drain into a shallow container and look for water in the fuel. It will be under the gas. If you find water, empty the entire tank and remove the fuel bowl. Use compressed air to dry the tank or just let it sit in the sun.

If this is too much to do, drain the fuel tank and loosen the bolt on the bottom of the carb. Get as much fuel out as you can. Leave the bolt loose and put some fresh gas into the tank. Allow a teaspoon or two to drain out of the carb. Tighten the bolt; don't overtighten. Try to start.

If that doesn't work, then you probably have dirt in the main jet. Look at this post for pictures of the various jets. Scroll to the bottom.

http://forums2.gardenweb.com/forums/load/lmower/msg061811009450.html?10

Bill K. - model and serial # in picture
Baymee - will try that in the morning...at work now
Thanks to you both.

The reason that lawnmowers can be hard to start, at the beginning of the season, due to evaporation. When the mower engine was last operated, in the fall of 2012, it was turned off, and put away for the winter. However, there was still some gasoline in the carburetor, and very slowly, over the winter months, most of it evaporated away, leaving residual gunk in the carburetor. The gunk is clogging up some tiny passages in the carburetor, so the gasoline can't get from the tank to the engine. To avoid this, some folks like to disconnect the fuel line and completely drain the carburetor at the end of the mowing season. Since there is no fuel valve at the gas tank, you have to plug the hose somehow and clamp it tightly, or else any gas in the tank will leak out all over the garage floor. Sounds like a hassle, so most people put the mower away exactly as you did last fall.

"Bill K. - model and serial # in picture"

There's probably millions of bacteria in the picture too, but I can't see them either.

I think this is one of these awful plastic carbs. The bowl comes off w/ 2 7mm screws. The large white emulsion tube comes out and gets probed clean. I haven't had much experience on these until this year. 2 had rough spots in the fuel tanks that appeared to be deteriorating.

Ok, so i opened up the fuel line and that was clean and inside the carb was spotless. Needless to say, i was baffled..... until my kid pulled on the throttle lever at the handle and i noticed the valve inside the carb didnt move.so i started to backtrack and i know its the throttle somewhere.
Pull the handle and the spring in the picture functions fine but not the valve in the carb. But if i pull the lever just outside of carb the valve works perfectly.
So, this is why it kept dying after a few seconds...only gas from primer was getting in.
My question, do i need a whole new throttle setup of is thia an easy fix?

Ok, so i opened up the fuel line and that was clean and inside the carb was spotless. Needless to say, i was baffled..... until my kid pulled on the throttle lever at the handle and i noticed the valve inside the carb didnt move.so i started to backtrack and i know its the throttle somewhere.
Pull the handle and the spring in the picture functions fine but not the valve in the carb. But if i pull the lever just outside of carb the valve works perfectly.
So, this is why it kept dying after a few seconds...only gas from primer was getting in.
My question, do i need a whole new throttle setup of is thia an easy fix?

{{!gwi}}

Ok, so i opened up the fuel line and that was clean and inside the carb was spotless. Needless to say, i was baffled..... until my kid pulled on the throttle lever at the handle and i noticed the valve inside the carb didnt move.so i started to backtrack and i know its the throttle somewhere.
Pull the handle and the spring in the picture functions fine but not the valve in the carb. But if i pull the lever just outside of carb the valve works perfectly.
So, this is why it kept dying after a few seconds...only gas from primer was getting in.
My question, do i need a whole new throttle setup of is thia an easy fix?

{{!gwi}}

Your picture is of the blade brake mechanism and isn't related to the carburetor at all. It's probable that you don't have a throttle cable at all.

Take a close up picture of the model number and the carb. I still think it's the carb.