Hey Zen
Looking at the pictures of the RT-3, it DOES have Reed Valves, as Red01 suggested, otherwise looks very close to my old 250.
Comments stand, great reliable bikes in their day. NOT overly powerful, but I still rode my 250 on the secondary highways. Quite heavy and not great handlers (compared to newer bikes.) Flexible frame at the swingarm pivot, and flexible swingarm as well.
Remember, Yamaha upgraded the dirt bike line to the revolutionary (in it's day) "monoshock" starting in the late 70's. You might not find any decent used shocks/swingarm that will fit. Forks wouldn't be a problem...
But, if it starts and runs well, and you take it for a ride, you might like it, or hate it. I loved my old bike at the time, but I know I would NOT want it now. By 1982 everthing had better suspension and handling.