While I have never done the rings on a 142F, every engine I have rebuilt, 2 stroke or 4 stroke, the piston rings have a specific top and a bottom to them. You need to be sure that they are installed correctly. Installing them up-side-down can cause excessive oil consumption as while they are scraping oil off of the cylinder wall they cannot keep the oil below the combustion chamber.
Another thing that you will be fighting is the cylinder. When the engine is brand new the honing process leaves a cross hatch finish on the cylinder wall.
This finish serves 2 major purposes:
1: The valleys in the cross hatch finish trap oil for proper lubrication during the break in process.
2: The peaks in the cross hatch finish act like a file that perform final shaping of the piston rings and conform them for a near perfect seal between them and the cylinder wall.
A light honing of the cylinder will greatly improve the break in of the new piston rings.
Obviously worn out valve train can cause oil consumption too, but you can typically see the oil trail going down the valve stem and crusting on the valve head if you look inside the cylinder head port. Also, on the intake side the port walls will have an oily residue all over it near the valve pocket.