I've been studying the Zundapp KS601 Service Manual.
Some seriously "Old School" engineering going on here:
(Good thing I still smoke occasionally)
"If too much material is ground off the big end when adjusting, attach 1.5mm wide tinfoil strips to these parts of the connecting rod (27) as a chuck. Cigarette tinfoil
is about 0.01mm thick. Tinfoil may under no circumstances extend into the bearing tracks or protrude at the sides."
Figure 27 -> = here tinfoil
Connecting Rod Adjustment:
"For the adjustment remove the connecting rod as specified. Put a piece of polishing cloth on the surface plate and on that whet the joints of the big ends one after another (25). One face has to be on the polishing cloth and one on the blank plate (25). Count every stroke to get even abrasion on both sides. Recommended are 20 strokes on each side before reinstalling the connecting rods.
In most cases this procedure has to be done 4 to 5 times to achieve an optimal fit."
A lot of the tools seen in the manual look like old carpentry tools.
I'm starting to get a little scared. My woodworking skills are pretty poor.