hi my name is jacob i am 15 live in texas and had just started to learn to ride on a 1973 honda xl100 but dont have access anymore to it so i just aquired two old yamahas! what i got is a 1971 yamaha JT1 j mini enduro that i am going to get running first becouse requires the least work and money. the other bike is a 1975 DT 175 a that will be a long term project so i can ride on the road when i am 18. i am trying to figure out what the "j" for the JT1 and the "a" for the DT 175 means. any help would be great.