Hi. I get the feeling that the oil in your petroil mix may not have been properly mixed, and you are getting a VERY oily mix at the moment, too viscous to flow properly through the carb, necessitating excessive use of the choke to get enough petrol in for the engine to run, but this means that even more oil is being drawn in ! Initially I would take off the exhaust pipe and check that the flange on the pipe is dead flat. If a little distorted it can be remedied by holding the pipe by hand onto the belt of a linisher. When you know it is dead flat refit it to the engine using a new gasket with a thin smear of exhaust cement on both sides of the gasket.
Drain the tank and the carburettor, and refill with ethanol-free petrol such as BP Ultimate. Don’t bother with oil in the petrol. If your oil pump is in good condition it should be very easy to adjust when used with the speed reducer.
Try again, and let us know how you get on !
Brian
