Mower sat for 3 years....changed the oil / drained the old fuel / cleaned the air filter / new plug . It started on the 1st pull and is running fine. Is there an inline fuel filter on yours? maybe plugged? Have you got a good spark?
I don't know if it will help...see page 3-15 excessive smoking in the following link to another lawnboy forum
https://www.mytractorforum.com/threads/lawnboy-diagnosis.646945/
I think I will be using Shell Nautilus 2 stroke oil when my supply of Lawn Boy oil runs out. It is recommended for air cooled engines. Alternatively, Castrol Go 2T motorcycle oil.
White smoke or black smoke? If black likely engine is running rich. Is underside of deck oil covered.....I have heard that it may be a leaking crank seal on other discussions. What are you using for oil and mix ratio?
Not sure if this is correct but this is what found using your model #
https://www.mytractorforum.com/threads/lawnboy-suburban-wpm-service-manual.646465/#post-6007553