Small Engines (Lawn Mowers, etc.): McCulloch BVM 240 Blower/Vac, fuel starvation, starvation problem

Question
My problem is this. From cold the unit will start. It works well for approximately 3 - 5 mins. it then stalls out as if fuel is not getting through. it doesn't cut out clean it seems to stumble and stutter. It will not restart until it has completely cooled down.
New Spark Plug fitted. New gas and old mixed to 40:1 added.

Answer
It sounds like a fuel starvation problem, if it runs that long, the fuel tank vent might not be working, to check, get it running again,
and when it starts acting up, loosen the fuel cap and see if the engine starts running better.

If not, removing the carb and dis-assembling, and cleaning are the
next step I would take, but try this first.

Thanks,
Fish