Main bearing half
upper, red
The 998 cc A-plus series engines was equiped with colour coding main bearings from approx 1989 on. This bearings was not a set, the halfs was colour coded, matching to the engines colour coding by a special overview. No oversize was used, cause it was OEM.
If your engine needs overhauling, in most cases oversize is neccessary and a grounddrilling is recomended, so use the main bearing kits recommended from approx 1983 on (lower half smooth with center location lip, upper half with groove and oilhole).
The 1275 cc A-plus series engines for Austin Metro etc. the colour coded main bearings was introduced approx 1989 too, for Mini with the reintroduction of the 1275 cc in 1991. For engine overhaul you have to use the recommended bearings from 1984 on.