I am working on a Red Wing water cooled kit from PM Research. I had an issue getting a drill to run true when drilling the flywheel hub prior to boring and reaming. On the second flywheel I noticed a strange pattern on the face of the hub after I took a facing cut. There is a light colored disk about 70% of the diameter of the hub that is offset from the center of the hub. there are 6 small diameter dark spots inside of the light area. If these spots are of a different hardness it could explain the issue with drilling. I asked PM Research and they stated it was from part of the casting process but did not provide any explanation of the process that gives this issue. Does anyone have any info?