Originally Posted by Rupe
Ok - might give that a try. Thanks
I'm trying to picture where these o rings are in the system but the issue sounds like fuel starvation but as it's not happening the moment you start the engine but only after it has been running a short while and then it takes a while to get going again then my guess would be that this is linked to the fuel in the carb pot. Ie when that is full because you've manually pumped it full from the tank or it's had time to be fed in from an internal tank the engine runs fine but you're burning the fuel quicker than it is being replaced. The symptoms sound similar/same as when we forget to open the fuel tank breather for example.
If you use an external tank then you could test this by reprising the bowl and carb after it has stalled to see if it fires up nicely again.
The o rings may be the cause as they could be causing a vacuum to fail that is required to draw fuel but it could also be caused by a dirty fuel filter, a failing or failed fuel pump, collapsed fuel line, tank blow large etc but as Fen suggests, there is no point in looking any further until you've got a good seal back on the carb and ruled out what seems likely to be the culprit of excess fuel isn't supposed to be dumped but returned to the system.