I have a couple of Clymer service manuals for sale;
Suzuki RM50-400 1975-1981
Yamaha XT125-250 1980-1983
$10 each plus postage
Also have a range of RM50 and RM80 parts lists but they are in Japanese, OK if you can identify the part from the diagram
RM50, RM50-2,3,4,5,6
RM80-3,3A,4
$5 for the lot plus postage