and what type of bearings did you get, exactly?
sadly, when it comes to crank bearings "same size" is NOT necessarily the same!
theres ABEC ratings, for starters, then theres another set of tolerances to be aware of.
sure, you may have walked into a bearing shop and gotten the "same" bearings, but just because they were 6302's or whatever the crank bearings are...doesnt mean it was a good idea. the shop holds standard bearings of standard sizes...not special tolerance bearings for specific uses. such as crankshafts.
sheesh, i want some angular contact bearings for my milling machine spindle...turns out theres four different varieties of the same size, each with different contact angles... most shops will carry only ONE. and they look at you strangely when you ask for a specific type. salesmen/disinterested employees versus industrial engineers.
check for those little washers/shims on the crankshaft itself as crassius mentioned.
did you remember to install the gasket between the cases?