The R2J and R4J are Mk1 MC18's from 1988, the R5K and R6K are Mk2 MC18's from 1989. The MK2 MC18 RK's were fitted with a PGM II, this had a 3D ignition map (but only says PGMII on the box), where as the RJ's from 1988 were fitted with a type of PGMI.

The MC21 is fitted with a PGMIII but still doesnt say 3D on it.
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If I have to take the carbs off once more...