K&B .61 runs rich then lean

[yesandbut]

I have a new old stock .61 with perry pump and carb that has a repeating behavior I don't understand. When I first start it, it runs slobbering rich. So rich, I can't go to full throttle with out it dying. I have to lean the needle about 30 degrees of rotation, and then I can fly. After about a minute I can hear it leaning too much so I have to land and return the needle to it's original setting, then I can fly the rest of the day. The next flying session, a week later, the same pattern repeats. Is this normal? It's a pain! Any help will be most appreciated, any of you guys that remember running this engine, back in the day.

p.s. I'm using 20 % oil, syn. and castor, 10% nitro. About 1 1/2 gallons of fuel through the engine. 11 - 7 1/2 prop, on a Bridi super kaos. Elevation is about 2400. Pump is set so midrange sounds properly rich/lean.

Best regards,
Chris

[MECOA]

Pumps that old usually don't work from deterioration of the internal parts.

This is not usual but you are lucky the pump is still working.