Hi ,
Is this engine a 2 stroke or a4 stroke , if a 2 stroke 30 weight oil should be fine
Make sure oil feed rate is correct on calibrator oiler and do these engines have a sump drain if so make sure it is operative and if all okay I would not worry about the smoke if its a 2 stroke a least you know its getting oil , I have seen many an engine fail by reducing oiling to have a smoke free exhaust , my view is oil is cheaper than engine rebuilds
Sunshineman