Flying Horse 48cc/66cc/80cc 2-Stroke Motorized Bicycle Engine Round Column Bolt &ndash; Gas Bike Small Bevel Gear Retaining Bolt The Round Column Bolt holds the small bevel gear on most 48cc and 66/80cc 2-stroke motorized bike engine kits Installation may require extra tools: first remove the stock bolt from the small bevel gear (note: this is pressed in, it will be extremely difficult to remove it with a flat-head screwdriver). Thread the new round column bolt in to the center of the small bevel wheel and table-or-machine press the bolt