ORIGINAL: Cyberwolf
I have been drilling and tapping hole's like this for more years than I want to remember and you can most certainly get it off center if done wrong. The hole may not be the culprit if the face is off is will cause the same effect. If you can't get any results give me a PM, i'm sure that we can come up with a quick easy fix and get you back on track.
That is what I have been thinking. maybe where the crank extension bolts to the crank shaft that may be where it is off if the hole is drilled in the center that could cause the same problem. Never really thought about that. My simple mind can only think in one dimension (hole drilled off center). Not sure how I would check that. Thanks for the heads up.