I attached a PDF that talks about servicing your vintage Elgin. Maybe it will be of some help; if not with the issue at hand….then perhaps with other issues you encounter.
As for the oil mix; I would run 16:1. The general rule is that engines with bushings as opposed to bearings in the powerhead need more oil. The newer engines with roller bearings are the ones that can run on 50:1 and the like. People on here swear by the new synthetic TC-W3 oils in the pursuit of less smoke; I have not yet tried it.
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I find that my engines smoke very little (even with 16:1 conventional oil) when out on the lake. Smoke can be obnoxious when barrel testing though.