Hi fella's, complete newbie to ride on mowers here, just been gifted a ride on mower, don't know what make, but it has a Briggs and Stratton 13.5hp single cyl petrol engine and a twin cutting deck driven of the bottom of the crankshaft (or not in this case)! By a pulley and drive belt. It's all there and all looks ok but when drive to the cutters is selected, by a seven position lever for different cutting heights, the drive pulley on the crank is not turning for some reason, drive to the wheels works perfectly, I should mention the mower hasn't been used for a couple years, any opinions appreciated, thanks