I think 1983 was the first year these came with watercooled motors.
They continued up to and including 1985 model with drum brakes.
The numbers don't match anything I have for Suzuki 80s.'The numbers aren't worn or rubbed out at all?
The numbers I have, read; 1RD13A-D-100001 for 83, up to 1RD13A-E-100001 for 84.
Unless someones put one of the above motors in a 1981 model frame?? Even then the vin number would read 1RD11A-B-100001