First you need to check to condition of the air filter. If the element is soiled then fit a new one. Secondly, if the problem still persists then it's likely to be a worn float valve letting in too much petrol into the float chamber. In that case you will need to obtain an overhaul kit. The carb needs to be in good working condition before any other adjustments are made.
I am not familiar with the type of carb fitted to your model especially if it's a French home market TL.
