It seems the older fiches are getting less helpful. I have trannies out can send a gear.
It seems that #20 1st gear wheel is the same for all years.
Yamaha 306-17211-00-00 GEAR,1ST WHEEL is used on these models and components:
1970 XS1 TRANSMISSION
1971 XS1B TRANSMISSION
1972 XS2 TRANSMISSION
1973 TX650 TRANSMISSION
1973 TX750 TRANSMISSION
1974 TX650A TRANSMISSION TX650A - XS650B
1974 TX750A TRANSMISSION
1975 XS650B TRANSMISSION TX650A - XS650B
1976 XS650C TRANSMISSION XS650C
1977 XS650D TRANSMISSION XS650D - E - E006501- - F
1978 XS650SE TRANSMISSION
1978 XS650SE-11 TRANSMISSION
1979 XS650SF TRANSMISSION
1979 XS650_2F TRANSMISSION
1980 XS650G TRANSMISSION
1980 XS650SG TRANSMISSION
1981 XS650H TRANSMISSION
1981 XS650SH TRANSMISSION
1982 XS650SJ TRANSMISSION
1983 XS650SK TRANSMISSION