Flying Horse 2-Stroke/4-Stroke Motorized Bicycle Chain Idler Pulley With Bearing Wheel &ndash; Gas Bike Chain Tensioner Pulley The Chain Idler Pulley with Bearing Wheel is an upgraded chain idler pulley for smoother riding compared to the stock idler that comes with most bicycle engine kits Installation is a breeze: unbolt and remove your stock idler, bolt this pulley to your bike frame, adjust your pulley to your chains needs, and you're ready to ride