Lawn morwer white smoke when starting and again when turning it off. Does this hurt it. Do i need oil
Could be that the lawn was wet and that the white smoke was actually steam.
A blown head gasket
white smoke almost always means your lawnmower is burning oil. this could mean either your piston rings are worn and need to be replace ( can be done easily if you have the tools) or you have too much oil in the motor.
lack of air or overfueling although there are many causes of both
When was the last the blade was sharpened? You may want to try sharpening if it has been a few years.
one of the causes of all three symptoms is a bad fuel injector
Injectors, timing, low cylinder pressure.
When you overfill oil in a lawnmower it will smoke when you tip it sideways while mowing,it has no harm
To much oil. or the valve stem is loose and its leaking oil
Many of them do
the valve guides could be worn out The carburetor is running fuel rich and needs adjustment. If it were valve guides or rings the smoke would be blue