The function of the cam chain tensioner maintains proper tension on the chain,chain tensioner is located under the timing chain cover on the front of the engine,its cog is connected to the chain drive with an adjustment to give the chain some stretch so as to gain optimum slack and tightness to the chain operation. Usually this device,there are three main types of camshaft drive used in motorcycle engines:roller chain, gears, and toothed belts.The aprilia uses a roller chain. When the tensioner fails, the loss of tension can cause the belt and pulleys to make high-pitched rattling or chirping noises. If the pulley bearing completely fails, it can also cause a squealing or even a grinding noise.meanwhile,you should inspect your tensioner in time to monitor its condition and replace it.