Will a cylinder off a 1975 Yamaha TY 175 fit a 1974 Yamaha MX 175?

I think it will. If you look at biebandit.com and find the oem Yamaha parts for the motorcycles in question and check to see if they are the same part number, if they are then they will interchange. you can crosscheck different years too if you found a 1975 ty 175 cylinder for your 1975 dt 175. So check out bikebandit and see for yourself, they are the next best thing to a Yamaha dealer.