Here is some info on how I trenched the case for a 4mm Stroker. Setting up mill to locate on bearing. Use the bearing to locate the center of bore not the case.
I bored it .030 inch at a time then put crankk in bearing to check clearance. I used a .020 dia wire for final clearance. A feeler gauge wont work here. I measured the width of the rod end plus .060 and divided by two for depth of bore.
