I have a Troy Bilt Horse s/n 109117 with a 7hp Kohler. I'm 99% sure about the model, finding a manual for it with pics that look just like my machine. I went to replace the belts following instructions in this manual which said "simply" remove bolt from reverse disc and remove reverse disc. My problem is that the disc won't simply remove. It doesn't look like a seperate disc at all, looks like it is part of the engine pulleys. Furthermore, there are three small allen head screws running through the disc and into the pulleys. I can't find a manual or part illustrations anywhere showing me the screws. Have I got my model number wrong? wrong manual? wrong belt changing instructions?