What Causes Abnormal Noise in the Scooter Transmission Box?
1 Answers
Here are the specific reasons for abnormal noise in the scooter transmission box: 1. The noise only occurs at idle or low speed: Possible causes include excessive clearance between the piston and cylinder wall; overly tight piston pin or connecting rod bearing assembly; excessive clearance between the tappet and its guide hole; wear on the cam profile of the valve train; or a loose starter clutch causing pulley noise, which becomes noticeable when the speed changes. 2. The noise becomes chaotic at a certain speed, with brief sounds occurring during rapid deceleration: Possible causes include a cracked camshaft timing gear or loose fixing nut; broken crankshaft; loose piston pin bushing; excessive axial clearance of the camshaft or loose bushing. 3. The noise appears during rapid acceleration and persists at high speed: Possible causes include loose connecting rod bearings, melted or mismatched bearing shells causing rotation; loose crankshaft bearings or melted bearing shells; broken piston pin; or broken crankshaft.