Walk behind TWO PUSH BEHINDS SAME PR0BLEM

[target75]

I recently had two different push mowers go down with the same problem within two days. They will easily start and will run normal for about 5 - -10 seconds and then will bog down and almost quit running and then will run normal again, they will do this over and over(no mowing at this time). One mower is a sears craftsman with a techumseh 4 horse motor (about 15 yrs old) and the other is a briggs 3.75 motor about 10 yrs old. Both have been very reliable mowers and I have always drained gas every season. The one thing in common is one gas container. I checked the gas in the container, I do use stabilizer and did not detect any problem so I thought some dirt from the container may have fowled up the carb. So I started on the craftsman and cleaned the fuel tank, replaced the fuel line and cleaned the carb, used fresh gas from a clean container and it did not fix the problem. Since this did not have any effect I have not started on the briggs. Does anyone have any suggestions? Any help will be greatly appreciated!!

Thanks, Tom