If the thrust surface of the crank has been touched by a crank grinder to "true it", it MUST be hand polished with 500, then 600, then 1500 grit paper. Look closely at the thrust surface of a freshly ground crank, and you will see what looks like a saw blade finish on the thrust. Hand polish it out. Since I have been doing this, my thrust failures have almost dried up. Also, the main cap must be seated with a LARGE Wichita Wacker! BFH, ok, a big dead blow hammer. The crank must be wacked hard from the front, then the back of the crank. Most guys know this, but some forget.