I think the problem here is a missprint in the 500/4 parts book, the two bearings are actually different sizes, the one on the countershaft is a 57 mm diameter and the one on the mainshaft is only 52mm. If you look at the part numbers for the retaining ring for the two bearings they are both different, it clearly says 52 or 57mm. So the misprint is not the part no, but the 5205 std bearing no, one of them is wrong. I also have a 550 f2 parts book and it gives same part no for the mainshaft bearing, but a different one for the countershaft bearing, in this case 91002 283 000 and the retaining clip is still the same as the old 500 manual, suggesting the two bearings are different sizes despite still saying they are both 5205 bearings! Not sure if this helps or hinders!
