Honda Petrol Mower running problem - cutting out on high revs
 

I have had no problem with my Honda GCV135 4.5hp petrol lawn mower until today. The motor starts on full choke but then wants to immediately cut out unless I quickly reduce the revs to the tortoise setting - ie low revs. The mower will cut the grass, but put the revs up and the engine wants to cut out again.

There are no problems with the oil level or oil and petrol leaks. As I say, the mower starts over and over again without issue. I have drained the carb as well and the air filter is cleaned regularly.

Advice please!

Just to add that I use unleaded gas always and have not made any mistake with fuelling
Austen