Especially if you are converting it from ball bearings to tapered, it just never seems as smooth as I would hope. Have done it to the Blackbird and (2) 500's so far and every time putting the lower bearing race in I feel like I am fighting it the whole way.
silly question but did you ever measure the ID of both bearings and the OD of the shaft, the bearings on the ER500 triple are different by 0.5mm the bigger one being fitted to btm race. reason I say this is the part no's are the same as the EX,when I ordered them.
otherwise do the thermal cycling thing shaft in the freezer overnight bearing in the low oven to warm up. if your quick it just slides into place with minimum effort.