Briggs and Stratton 6.5 on a Craftsman deck, Run of the mill yype push mower.  Wont start.  Removed airfilter, poured gas onto carb...Starts/Runs.  I cut the lawn.  Stopped motor, tried to restart; no joy.  Primed again: Joy. Repete with same results.
New plug, no corrosion in carb or bowl, primer bubble intact.

Any ideas?

Thanks

Probably needs a good carb cleaning. Bad gas can do that to it.

Here's my guess.  It's a self-priming model with the float style carb.  At the bottom of the carb float bowl is a bolt.  Take the bolt out, it probably has some debris stuck in the small hole down by the base.  The bolt is hollow and drilled through, but since there is no inline filter, debris gets stuck in the bolt, that stops the flow of fuel to the carb venture.  I've fixed a bunch of them that had that problem.  Want a permanent fix, add a little inline filter from the tank line to the carb, something from napa, autozone, o'reillys.


ETA:  Didn't read your post thoroughly.  If it has the older diaphragm style carb, the thing that goes bad most often is the diaphragm, which is also the fuel pump. No matter the make or model, removing the carb and spraying all openings, jets, etc out with carb cleaner can't hurt and might be all it needs.

Good chance for your symptoms.
Sounds like your auto choke is tits up.

You are bypassing the choke system when you prime it by hand.

FW_wife had this problem after Fatalwishes died.  I just sprayed some starter fluid in there, it started right up.  Never had a problem w/ it since.  

When did it last run? I had a similar issue as in the video posted above, but my spring was fine. I removed the cover and there were enough cobwebs in there it wouldn't work. The choke opens with vanes using the wind caused by the flywheel so as the engine comes up to speed it opens the choke.

I have a question.  Anybody have a lawnmower that starts (usually) fine, and then dies the minute it hits grass, or when you push and then pull it back, like the pulling motion does something to the engine/fuel?