Lot’s of very good advice here. I run my K&B 61s on 5% nitro and 22% oil half of which is castor. However, the engine should start and run fine on what you have.

I assume the fuel is fresh and there are no air bubbles in the line when you choke the engine. True?

The engine sounds like it’s starved for fuel. Sometimes, in this situation, I just go ahead and open up the needle another 1/2 to full turn and see if anything changes.