I would check for chain stretch and if acceptable check the injectiom pump timing. Should be done anyways on any unknown engine of this type.

Late injection could add to smoking as combustion is less efficient. Especially before operating temperatures are present. You also do not want to be driving around with a massivly stretched timing chain. This does not mean it is the fault itself causing your issue but you have to start somewhere. I assume your air filter is not totally shot as well.