Piston to Cylinder Wall Clearance: 
Wössner pistons are designed with a special cam 
and cylinder design. When measuring for piston to 
wall clearance, measure at widest point of piston 
skirt from the bottom of the oil ring groove, 90 
degrees from wrist pin hole. 
Coated Pistons: 
Piston to wall clearance is calculated before the 
coating is applied to the piston skirts. 
Dome Clearance: 
Dome to cylinder head clearance need to be 
checked prior to assembly. 
Valve to Piston Clearance: 
Most Wössner pistons are designed with valve 
pockets that are deeper and larger than OEM. 
These pockets provide adequate valve clearance 
under most conditions. It is very important that 
valve to piston clearance is checked upon piston 
Installation. This is necessary due to many variations 
in cams, how much a block has been decked, 
or if the heads have been cut or angle milled. 
Installation instructions 
4-stroke rings 
The rings are installed with suitable piston ring pliers, 
starting with the lowest ring. Excessive opening of 
the rings is to be invoided, since this could lead to 
deformation of the rings. If the rings are deformed, 
they are not longer able to provide a perfect seal. 
Rings that have the mark are to be fitted with the 
marking facing upwards towards the piston crown. 
Special care is needed for the installation of steel rail 
rings (3S-rings). 
After the spring has been loaded, the rails are to be 
mounted so that rail end gaps point towards the 
pin hole. When the upper rail is being installed, the 
ends of the spring needs to be held together so as 
to prevent over-lapping. After this, the lower rail is 
to be installed. In the case of pistons with rotation 
prevention in the ring grooves, care need to be taken 
to ensure that the ring gaps are positioned alongside 
the location pins. After the rings have been installed, 
the ring gaps are to be spread evenly around the 
circumference (for example at 120° intervals for a 
3-ring piston).