i'm replacing the drive belt on my mower which is probably 10 years old. in order to remove the belt from the pulley thAT'S attached to the engine drive shaft i removed a screw under the lower pulley and both pulleys are supposed to slide off the shaft. the pulleys are mounted with a spacer between them. I HAVE TO LOWER THE PULLEYS TO get the belt past the belt keepers. the lower pulley runs the mower deck. any suggestions how to do this?