Outdoor Power Equipment and Small Engines - problems with my craftsman lawnmower

hi i have a craftsman riding lawn mower model number 917.270810 19.5 hp 42 inch cut. This year when I'm cutting the grass, after running about 20mins or so it stalls, I can fire it back up and it will run for about 5 mins and dies out again and so on. So the other day when this happened I took the hose and cooled off the engine and when I fired it up it stayed running, so i'm thinking that its over heating. So my question is what would cause it to overheat and how can I fix this problem. Also I want to change the plugs on it but i'm not sure what kind of plug i need or what gap it should be. thanks for you help

Check for the engine numbers, should be a small placard on top of the engine shroud and verify that 42e707-2631-e1 is indeed your engine.
This problem can get a bit tricky to diagnose. If you can get it in a no start condition, check for spark. If you have spark and it will not run, then we can help you troubleshoot it further prolly checking for fuel flow. If it stops and you show spark make sure it still will not start.
For the spark plug you can remove one of the current plugs to get a number, gap should be .030.

If you use or confirm the engine numbers you can view or download manuals here Manuals, Parts List & Wiring Diagrams - Briggs & Stratton (http://www.briggsandstratton.com/maint_repair/manual_and_more/docsearch.aspx?enginelookfor=42e707-2631-e1)

So the other day when this happened I took the hose and cooled off the engine ....

Opinions: Is this really a good idea?

Opinions: Is this really a good idea?

In general, no. I don't think it is really "over" heating.
It does bring up a good point though, this is an air cooled engine and the cooling fins under the metal shrouds should be cleaned and cleared of debris and build up. Compressed air is a good way to clear it.
Engine oil also helps in cooling so make sure the level is at a safe point.
The operators manual at the link I provided should have info on cleaning and routine maintenance.

I am having the exact same problem with my Craftsman riding mower. It will run for about 15-20 minutes when I first start it up and then it spudders and stalls. then I can start it back up but after a few minutes it stalls again and again. I have replaced my fuel filter, air filter, spark plug, and sprayed carb. clearner and checked the oil level. There are alo no blockages in my gas tank. I checked the gas cap and it seems fine. I have no idea what else it could be beside the carb. Please advise.

I am having the exact same problem with my Craftsman riding mower. It will run for about 15-20 minutes when I first start it up and then it spudders and stalls. then I can start it back up but after a few minutes it stalls again and again. I have replaced my fuel filter, air filter, spark plug, and sprayed carb. clearner and checked the oil level. There are alo no blockages in my gas tank. I checked the gas cap and it seems fine. I have no idea what else it could be beside the carb. Please advise.

Same as above...check for spark when it will not restart.

It always starts right up. It just stalls while riding.

This is a symptom of a coil/magneto failing. It is hard to confirm and there is no positive test for the coil especially when its working. Being an electronic part its not returnable. Other than trying another coil, or checking for spark when it will not run, I personally do not know any other way to determine it.
If you have or purchase an inline spark tester, you can install it and let the engine run until it dies and watch for spark. Thats about the easiest way I know of.
Dere is lots more smarter folks here than I however, ;) perhaps someone else has some tip.

Sorry :o

I read another post with a guy with the same mower as mine with the same problem, and he was told to try to run it with the gas cap loose. So today when I was cutting the grass and it stalled for the third time, I loosen the gas cap and it seemed to run fine the rest of the time. So now that I figured out whats causing it to stall, how do I fix the problem or do I just leave the cap loose. thanks

Replace the cap. The vent in it becomes clogged and causes your problem.