I have a Troy Bilt Model 12A1836M011 100905 serial # 1C048KC0084. I replaced the self propelled belt pulley on the motor shaft and now it only runs in slow speed. It has three speed levels but when I shift to the second or third , it stays in the slowest level. Is there an adjustment I'm missing where the cable hooks to the pulley housing? I can't locate a manual on the on line site for troy bilt . Thanks charlie