Most likely your 2T oil consumption is too high. Have you ever
measured your 2T consumption? Do you see a lot of white smoke
coming out your exhaust, even when the engine has reached normal
running temperature?
For SP, 1 litre of 2T for every 40-50 litres of petrol is normal.
The factory setting is even lower, about 1 litre for every 70
litres. Try to adjust your pump, then see if there's still black
oil coming out from your muffler.
