I bought a used Saito 120S and I am in the process of cleaning it up. It needed new push rods, gaskets, and screws.  What side of the rocker arm does the rocker shim go?  At first I placed it on the slotted end of the rocker arm retaining pin.  But with it in this position the valve end of the rocker arm is not centered over the valve stem. Looking at the exploded parts view it looks like it goes on the threaded end (drawing not clear). It appears this would center the rocker better over the valve.   One other question - I pulled the cylinder and the piston/rod assemble popped loose before I could look at it.  There is the letter "F" stamped on the rod.  I am guessing that this it front.  Also I am wondering if the piston has a front mark.

What say you Saito experts.  Thanks!