Lawnmower Engine will start, but then slows down and stops...

Have a pull start mower that was working fine until today. Got it started no problem (about 3 pulls) and got about half my lawn done. Stopped it twice to empty the bag and after the 3rd start (both 2nd times started right up) it was working fine until I hit some heavy grass and it bogged down I pulled back but it stopped. But when I went to restart it it started fine but with a few seconds it started to slow down and then stopped. Working the throttle doesn't seem to help (if I feather it it will keep running a little longer, but still stops). One thing that is interesting is if I rock the mower back and forth or side to side it will rev back to normal speed so something tells me I have some sort of fuel flow problem. Let it sit for over an hour with no change.
Cleaned air filter, oil looks good, had just filled tank with fresh gas (although when I started it it seemed like some gas did leak out from under the cap).
Unit is 12 years old.
Any ideas on what to check?
Thanks
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I came looking for a similar answer, and will continue to do so, but if the gas cap is on too tight, this is what happens. ( I think gas caps are made to vent, however, they don't always work that way)
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Thought of that, just got back from trying a few other things.
Took gas cap off, same problem, but now it didn't even want to turn over. Priming it will get it to start, but now it will just start, run until the gas is gone from the prime and then stop. It is like it isn't pulling any gas into the carb once it starts to run.
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Probably some bits of grass clippings in the tank or carb.
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On Thu, 20 Jul 2006 18:25:41 -0400, "ng_reader"

To test the cap, put it on loose, then wrap a little duct tape around the cap and tank so it dont fall off and get chopped up.
You might have too much grass, or some twine, or whatever entangled around the blade and crank. Remove plug wire, flip the mower over and check. Put wire back on.
OR, you got a plugged gas filter, bad gas hose (collapsed), or clogged carburator. Take hose off carb and see if gas runs out. Replace filter (if there is one). If there is no clog or bad hose, take the bowl off the carb. They tend to fill with crud. Clean it well an replace it. You may need a new bowl gasket, but I have reused them too.
Hope this helps.
Mark
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Dnt "flip" the mower over unless you want base oil to enter the combustion chamber via the crankcase vent.

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John Lawrence wrote:

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On Fri, 21 Jul 2006 05:14:18 -0500, snipped-for-privacy@UNLISTED.com wrote:

Radio Control Aircraft/Paintball Physics/Paintball for 40+ http://home.comcast.net/~dyrgcmn /
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