Wish I could help but am new to this kind of repair.Don't give up to soon the people on this forum want to help. They may need more details. It took me a week to get enough information for them to be able to help me.

Mike

if it looks bad it probably is IMO> What do you have to lose by replacing the vacuum hose and fuel lines probably the cheapest of all your parts you replaced. My best guess is once the heat builds up in the heads the vacuum hose starts leaking thus pumping air in the fuel pump which migrated it way to the carb. Did you find anything in the carb. the other 4 times you cleaned it??? if so I would clean the tank out and replace fuel hoses. sometimes fuel hoses rot from the inside (especially in high heat areasdown stream for the filter)and little pieces of rubber migrate that way to the carb. did you see any of this in the carb bowl??

outside chance Could be the fuel pump getting weak.

Definitely repair the vacuum hose. It might be sealing erratically enough to ALMOST power the pump sufficiently.

Check fuel tank venting (gas cap?). Maybe it's restricted enough to where you are pulling a vacuum in the tank.

Yes I did clean the fuel tank and the line from tank to the filter, all the other lines where replaced last year.

First time I cleaned the carb I found rust in the bottom of the bowl and removed it. 2nd time I cleaned the caarb I used scotchbrite on the bowl to clean it smooth. 3rd,4th and fifth time I completly disasembled it and clean out everything with carb cleaner making sure all jets and needles where in good working condition.

Fix the vacuum leak to eliminate it as a peoblem. If that does not do it....

1)Reality check: Put a spark plug tester in line with the spark plug. Does it get dimmer or go out when the problem occurs?

2)Does this have a manual choke? If so, does choking it help when the symptoms start (even a little)?

3) You might see if you can be borrow or steal another carb to try in place of this one.

The problem here is you don't know what's wrong, and so you go to replacing stuff that doesn't need replacing, and fixing stuff that doesn't need fixing. The truth is - we've all done the same thing at one time or another. It's the way untrained mechanics get things done, or not.

I used to supervise large construction projects, and we had a lot of heavy equipment. We also had a full time "backyard mechanic" to fix the small things that went wrong. Once he worked on a 20 ton yard crane for three days trying to get it to run. I finally realized he had no idea what was wrong, and called Cummings diesel. The guy came out and in less than 30 minutes found the problem. I learned something that day.

I learned it's easy to fix the stuff you know is broke, but sometimes when you don't know what it is - it's better to take it to someone who has seen it before, like a dealers service department, as hard as that is to take - it might turn out to be cheaper.

Yes it does help to pull out the choke until it chokes its self down. Replaced the fuel pump and fixed the vacuum hose from valve cover to fuel pump. Same problem, it has to be in the carb.

Have been working on 19Hp B&S with similar problem.I pulled the carb for what seems like 50th time this time I turned the carb upside down and with a small wire cleaned out the small hole just below the bottom throttle plate put it back on and the problem went away.I did this yesterday so I'm not sure about the long term effects. Good luck with yours. At this point any success helps.

Mike

My frind it can be as simple as your gas cap. If Your gas cap air intake is stopped up it will create a vaccum in the gas tank and you can't get gas after a few minutes of running. try leaving your gas cap loose and see if it still stops running.
Hope it helps, John

I've cleaned the carb with welding tip cleaners in every hole that is has and sprayed carb cleaner thru every hole and jets did not help.I've also ran it with the gas cap off did not help. And from what I can tell the gas cap does not have a vent hole anywhere.