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They do fit but depending on specific types (there are several) you should pay close attention to alignment of the valve tip as the exacting tolerances of YT outweigh GMH, with the different valve arrangement between carby heads and EFI heads the centring of the valves are slightly different.
you want the tip of the roller rocker to be slightly outward of the tip of the valve. the reason being, as the rocker depresses the valve, the tip will roll off the center and inwards. at full lift the tip of the roller must be in the center of the valve stem.