I'm gathering parts for my Murray Track II. I am going to change the drive system to a 35 chain and sprocket, so I ordered a 66t sprocket but it was just a plate sprocket, so I drilled it some, just to make it look better. I used a 1&3/8" hole saw, a 1" hole saw, and a 1/2" drill bit. I think it looks a whole lot better and it won't cover up the whole left side of the rear wheel.