Smoke show

THere's a good chance that you have now warmed the engine up to proper operating temperature and that nice warm oil has dissolved and eashed away the gum and varnish that was closing up the clearances in the valve guides and rings. It happens a lot on an engine that had been run hard, left to sit, and had infrequent oil changes over the years. As "OLD" said, the engine is probably now telling you the truth about its condition.

The advice about changing to fresh, correct weight oil would be a good first start, but you're going to have to diagnose the engine and that means performing a proper compression test, engine at temp, first dry and then include a teaspoon of oil through each sparkplug hole. It the compression is low dry, and significantly higher with the added oil, suspect worn rings. If low both ways, that generally points to valves. BTW, the guides in a two cylinder are generally ready to be replaced after 65 years. That was one item that tended to be overlooked in the interest of expediency and cost during top end overhauls in the past.

Another tell-tale sign of gum and varnish being dissolved is new evidence oil leakage around the left hand main bearing, behind the flywheel. Oil here can also mean you have high pressure in the crankcase due to poor venting.

So, next, you'll want to clean and test that the filter at the valve cover is functioning, and that the air tube from the governor to the carburetor intake elbow is clear. If the fumes can't vent properly, the pressure in the crankcase can increase (again, caused by poor sealing of worn rings allowing too much blow-by) and this pressure can push oil down valve guides and into the combustion chamber. They will smoke from that, just like a modern engine will from a plugged, non-functioning PCV system.

Lastly, check that the oil drain hole in the head is clear of gum and debris. If occluded, this trapped oil can rise high enough to actually roll into the valve guides.

sp, warm it up, drain the oil warm, and re-fill using a new filter and proper weight oil. Then you can service the vent system, check behind the valve cover, and if it still smokes, go to the shop and check the compression.

I'm betting you have worn rings and guides, but that's just a guess based on your description of the symptons.

Frank

Plus, as "old" is telling you, stop & immediately replace both the oil and filter element because you don't have a good feel for what is in your C/C right now.

For this time of year, when temerature is between 65 & 90 degrees, SAE 40 is oil called for in the Operators Manual. Use of any 10W-40 oil will do just fine. When winter comes, 10W viscosity is called out!

Be Blessed!