I know that there are already some bearing replacement and rebuild tuts on the site. I already looked and if this information is elsewhere, my apologies and I appreciate any navigation assistance that you may be able to provide.
So, I've got an old AV88 and am currently working on rebuilding the wheels. The rear bearings were easy enough to find replacements for. The front hub has bearing cups. The recess into the axle/bearing seat (sorry, weak on terminology here) is rounded to accommodate the bearing cup so I am assuming that a replacement bearing would bottom out at the beginning of the contour, at 10mm. The axle is also tapered where the threads start so, the left and right side diameters (d) would presumably be different.
Dimensions of the hub recesses and pics follow:
Brake side (d=inner, D=outer, B=width):
d=11mm, D=31mm, B=10mm
Speedo sender side:
d=12mm, D=30.5 (probably also 31), B=10mm
Bearing cup in pic is representative of the one I knocked out of both sides. Dimensions (cup and outer race) were:
d=15 (cup), d=21(outer race/lid/whateveritscalled), D=31, B=15 (rounded)
Maybe a 6200 or 6201 might work but would require a new axle.
I'm also guessing that acorn nuts would have to be replaced since they wouldn't be acting as a part of the outer race and packing the bearings into the cup anymore. Maybe just a flat washer behind a hex nut as a replacement?