Thanks for the quick reply. I'll see if I can take some pictures with the oil pump off and share them.

Sounds like you may be using too course a prop, which prevents the carby from transitioning to full rich? Also, check if you have sufficient fuel flow...

From the 'out of the box' department, could it be prop vibration/resonance? Has the prop been disassembled and perhaps re-assembled in a different pos...

Hello Doug, Any chance to ask the gurus at the factory about this? I have the oil pump off and like to know the best way forward. Thanks, Rob