Hi Min,
I dug out some Bearings, some old (very old) up to the latest to measure
I measured from the 'business side' of the Inner Race, to the 'Business side' of the circlip groove;-
I got a range over 5 bearings from 0.797" to 0.827" - a range of 0.030" over these bearings, keeping in mid these were all used bearings, so there maybe some wear, but they all still felt 'tight'. Also, I've measured these 'unloaded' (ie, without the 2 inner races being clamped up) so I suspect, when clamped up, these variations would come down a long way.
Just looking at the part numbers for this bearing from 1969 to the present day, there has been a few changes in these over that time, the first being 11MDJT1G, then a 3/MDJ1N, then a 1/MDJ25.4N (which looks to be just a metricated number of that previous), a CDU 1479, AAU1365etc etc, so apart from a metrification of the numbers, I'm unsure as to what the difference between them is, however, I have fitted these latest Bearings to everything, from the earliest to the latest, usually without issue, though I have ground a few (thinned the inner race) prior to cutting shims as needed to space the bearing closer to the Final Drive Pinion, usually only needing 0.020"
Coming back to your Bearing, at 1/8" (0.125") difference, that's HUGE and really has me scratching. Are you able to post up a photo?
I've come across the KOR brand Bearings, they are ~ OK ~ but there's no way I'd fit them in to a Gearbox!
There is a distinctive larger space between the two rows on bearings on the inside of the cage holder which explains the larger size.
..........as the Minisport bearing fell apart when I was dismantling the gearbox despite it only being fitted for a less than a month and probably 2 miles use.....
I'm just wondering here if the 2 inner races are actually and properly clipped together?
As I think you've found out, the Inner Race is actually made up of 2 Races and they have a C shaped spring clip that holds them together.
Also, in regards to the Bearing 'exploding' you'll likely find on disassembly, with the late Mainshafts, all Bearings will do this. The Bearings are an interference fit on these shafts (quite so) and so they are difficult to budge off the shaft once fitted. On disassembly, in the normal way, it's necessary (as you are aware) to slide this Bearing down the Mainshaft in order for the remove of the Shaft itself from the Box.
The early and early A+ types were a 'slide' fit. I found no issues from this type of fitment. Nowdays, with these later shafts, I take a lick off them with a diamond lap so the Bearing is a neat slip fit, no more exploding bearings.
