This season I've been battling the same thing - stalling after mowing fine for some time, and difficult to restart. I noticed air in the fuel filter, causing rough idle and ultimately stalling altogether. Long story short, I will be draining the fuel and replacing with 0% ethanol fuel that I purchased at Home Depot in a can (no stations near me offer 0%). Research has informed me that ethanol is the enemy of small engines. Ethanol blended fuels also have a higher vapor pressure, meaning that it will vaporize more easily, such as on a hot day, causing vapor lock. Making matters worse, I bought higher octane gas in the spring, thinking it would only be better, but no - they use even more ethanol to raise the octane, perhaps leading to my vapor lock issue. Using old blended gas could also lead to vapor lock issues since the ethanol separates out. I tried all other suspects, such as gas cap, spark plug, magneto, checking for clogged fuel line, flywheel key (timing), valve clearances, cleaning carburetor. I've gotten to know my Timemaster very well, but I'm hoping I finally found the cause to be as simple as bad fuel. Will come back with what I find.
