A timing belt system for an air cooled Twin Cam V-Twin motorcycle engine is provided. The timing belt system includes a crankshaft pulley assembly including a crankshaft pulley affixed to the crankshaft and a pulley flange affixed to the crankshaft pulley. The timing belt system also includes a camshaft pulley assembly including a spider gear having spindle affixed to the rear cam end of the Twin Cam engine and a hub having slotted apertures fastened to a camshaft pulley fastened. A timing belt having teeth is connects the crankshaft pulley to the camshaft pulley to turn the camshafts in synchronized rotation with the crankshaft. The spider can be rotated relative to the camshaft pulley and fastened thereto using bolts extending through the slotted apertures to Advance or Retard the timing of the camshafts relative to the crankshaft.