Firstly Id like to say i have searched the forum with no results.

I got a Victa powertorque to fix the type without the decompression valve on the head. Had old fuel so it should have been an easy fix. Cleaned carby/tank and started it up. Runs and idles fine although it does have the occasional backfire.
However when i rev it up it... theres no revs it just dies. Once the engine is idling i took the back cover off the carby and it revved just fine. I thought it might have been the big spring behind the diaphram so i replaced that with a stronger one... still not better.
The engine came with the poppet set at "C" so i left it at "C". I decide to change it to the other setting... Still doesnt work.

Next I had a look at the Top O-ring although this was probably pointless as the engine had already revd up.

I had a thought that the Vacuum button might not be in the right orientation.

Any ideas on the problem would be much appreciated