I don't know what you plugged up not familar with that model? So this is a guess at best. but, if it was the one way check valve from the crank case that pressurizes the bar oil tank, then the bar will not oil. I would guess that any rubber material in the system would be detoriated and therefore useless due to it's age.

IMO you will have to disassemble it and see what you got. My old lombard has a manual oiler it's like a pump on a bottle of windex, soap despenser, ect.. forces oil in the little chamber out through the oil feeder oils. if the pump plumger seal is bad it probably won't pump oil out.

I would think the only way for bar oil to get into the combustion chamber is through the gas/bar oil tank seperation wall, from either a crack or a bad gasket seal between the two. Or being drawn in through the crank case by the path of the bar oil tank pressure check valve or a crack sucking bar oil into the crankcase. A Little oil makes alot of smoke. also you need to look at any seal area between the bar oil tank and the crankcase a bad seal their might be letting bar oil being sucked into the crankcase and being burned when the piston goes up and down. Again I not familar with that saw, but have saws of that era.

My lombard was leaking between the tanks. I had to buy a sheet of gasket material. trace it out onto the material by laying the housing on it and apply pressure to leave an imprint then cut it out due to no manufactured gasket available.