Update....
When I reassembled the carb I set the poppet valve to the 'A' setting. I mowed for about 15 minutes on full throttle before the same problem of it starting the stall. I left it for the day then set the poppet valve to the 'C' setting.
Mowed with a full fuel tank on full throttle with no stalling. Re-fueled and mowed for another 15 minutes (I live on a large corner block) with full throttle.
I can't recall what the setting was before but would have been the 'A' setting as I recall the revs were lower than the 'C' setting. One thing I did notice is on the 'A' setting when it was idling the revs were very low but doesn't explain why it would suddenly start to stall after a while on full throttle when it was fine before. Anyway I may experiment with another poppet valve and see what happens.
Thanks for your replies.
