Compared to rivals that use a high-revving, high-output 2-cylinder engine, the MT125R was a single-cylinder engine that was disadvantageous in terms of output, but its lightness and compact size made it a weapon for handling and low-revving torque.

Furthermore, by improving it year by year, especially by cooling the engine with water using kit parts, the MT125R succeeded in pushing out the old rivals of the basic design. Hiroyuki Iida, an in-house team, won the championship in 1976 and 1977, and Koji Ueda, an RSC contract, won the championship in 1978, winning all Japan 125 for the third consecutive year.

In order to prevent the MT125R from playing an active role, Yamaha introduced the water-cooled single-cylinder works machine YZR in 1977, and also sold a replica of this machine, the commercial road racer TZ.

1977 MT125r