Welcome to the 1970 Yamaha AT1-B Forum. The factory paint color was called "Competition Yellow". The USA vin number range is: AT1-120101 to 138890. Feel free to post anything related to this model in the category. Anything new, will be added to this section. If you see any errors, please contact me privately.

                    1970 Yamaha AT1-B Specifications

            Model 1970 Yamaha AT1-B

Any parts for the 1970 Yamaha AT1B will be added here.

Hello first time on this forum. I just bought a 1970 Yamaha 125 enduro. Yellow tank. The engine case and frame calls it an AT1. It’s got 5600 miles on it. The stock piston is toasted. I’m having a really hard time finding the right 2nd over piston. I’ve received 2 both are wrong. To big by a lot. I’m obviously doing something wrong. I’ve bought a 285-11636-00-00 and 251-11636-00-00 both are like way ttoobig. Stock bore is 56mm witch is like 2 1/4 inch diameter just for an example. The ones I’ve received are like 2 5/8 inch diameter. I’m getting a mm gauge tomorrow. Point is what am I doing wrong? Any help would be very much appreciated.