If you hold the carb upside down with the float now seating the needle, can you blow air into the gas inlet with your mouth? If you cannot, look for another reason.

Did you blow air into the primer cavity with the bowl securely assembled? It is quite possible that you over-pressurized the bowl if you did in fact blow air into the assembled carb. This could have caused crushing/distortion damage to the float.

Yes, I can blow air into the fuel inlet and it does blow past the needle (with the carb upside down and the float pushing the needle into the seat). The float is plastic and the needle slides on/into a slot on the float. When the float is assembled onto the main carb body, it almost seems as if the float won't allow the needle to come in contact with its seat. It's a realitively simple carb with few removable parts. If I remove the pin that attaches the float to the main body and lower the float to allow the needle to seat, I have a 1/32" gap before the needle actually seats. That's my reasoning behind thinking I blew out a removable seat a something simular.

What is the model and type number for this engine?

I can't think of any Briggs engines that have a removable seat (other than the whole brass housing). Tecumsehs do have removable seats.

If you post the model and type, I will know for sure. I could be wrong.

Some Briggs needle valves have viton tips. It's possible that tip could have blown off.

What does the needle look like? Is it metal with a nice chamfered tip, or is it metal with a rubberized tip? Or it could be metal with a missing tip.

If it is solid metal with a nice chamfered tip, it's very likely that your application does have a removable rubber (or similar) seat.

The 7HP Briggs engine is on a Craftsman Walk-behind mower. The tag on the gas tank states: Family - YBSXS 1901.VE 275078. The metal plate above the muffler has the following number: 128602 0212 E1 020222 FA. The needle is metal with a chamfered tip - no rubber (unless it was blown across the garage) and the seat is drilled directly into the main body - no brass insert as far as I can tell (unless it was blown across the garage). I'm wondering if the needle had a rubber tip on it and it was stuck in the closed position. When I pulled the float and needle out, the rubber tip (if it had one) may have been stuck to the carb body. My original problem with the mower was the that it wasn't getting gas, other than the (3) pushes of prime on initial start. It would run for a few seconds (burn up the gas that was pushed in by the primer button) and shut off. There are no markings/numbers on the carb itself. Any thoughts?

Lawnjocky, yes, it sounds like you blew out the small float pin seal. Some carbs have rubber tipped needles and others are solid and have a small rubber seal in the base of the pin hole. If you used compressed air then more than likely you did dislodge the seal.

I'll head to the parts shop and see what I can find. Thanks for all your help!!

Yep, sure enough, your carb. has a little "donut" seal which the needle seats on.

Hmmm.... I learned something new. I've never seen a B&S with this setup. All the ones I have seen have had a viton tip on the needle. But I guess that I have mostly worked on Vanguards.

The needle and seat come in a kit.
B&S Part Number: 398188

If you used compressed air and blew it into the carb most likely you did dislodge the seat. It doesn't take much.
Just take it apart and use a dowel to gently push the seat back into place and check float action by blowing with your mouth into the fuel inlet. Obviously make sure the gas is out and the carb is off the engine.
Some people don't like this procedure because of the gas residue on thier lips. (SO WHAT !) but you can check the valve operation with as little air going through as posible.
You'll definitley feel when and if the needle and seat are working.

I have the same mower as Lawnjockey (Craftsman Walk-behind mower. Family - YBSXS 1901.VE 275078. The metal plate above the muffler has the following number: 128602 0212 E1 020222 FA). I was having a similar problem and decided to try to clean and rebuild the carb. Simple, I thought!

I purchased "KIT-CARB OVERHAUL" #494349 from my local dealer. Now, I need to figure out how to clean and replace. The instructions are total gibberish. Is there a good instructional video for this procedure? I couldn't find any. Also, I couldn't seem to be able to find a part number for the carb itself. That would be useful for finding some sort of instructions.

Any help with this would be fantastic!