I believe (seeing its a Poulan ...MAYBE a Briggs engine..?? ) what you are calling a double pulley is in reality is the "stack-pulley"
mounted on the engine to propel the mower, and also turn the deck blades , WE need some info. see example ..
My goof--up SORRY, got distracted while reading post, ..( glad that doesn't happen while I'm texting as I'm driving, might misspell something ) ..:laughing: ,,:laughing: