Reasons for Pedal Starting Shudder
2 Answers
There are several reasons for pedal starting shudder: 1. Poor Lubrication: Insufficient lubrication between the movable and fixed discs of the driven pulley in the motorcycle's transmission system increases axial resistance, preventing the movable disc from tightly clamping the drive belt under spring pressure. This causes the drive belt to slip intermittently when the driving pulley rotates the driven pulley, resulting in belt shudder and noise from impacting the transmission case cover. Additionally, the centrifugal clutch transfers power to the rear wheel through the belt, causing the motorcycle to shudder during startup. 2. Insufficient Chamfer: If the chamfer on both ends of the clutch friction plates in the centrifugal clutch is too small, wear over time eliminates the chamfer. During operation, the friction plates expand under centrifugal force to engage with the clutch housing. Without proper chamfering, engagement becomes uneven, leading to power transfer issues and motorcycle startup shudder. 3. Oil Contamination: Oil contamination on the working surface of the clutch friction plates or excessive grease inside the clutch can cause problems. Under high temperatures and centrifugal force, grease may flow outward axially and splash onto the clutch housing and friction plates. This results in abnormal slippage during clutch engagement, transferring irregular power to the rear wheel and causing startup shudder.
From my experience in car repair, pedal vibration during starting is mainly caused by clutch system issues. Severe wear or uneven surfaces on the clutch disc lead to unstable power transmission; scratches or burn marks on the flywheel create vibrations during initial movement; aging or failing pressure plate springs result in loose clutch engagement, transmitting vibrations through the entire drivetrain to the pedal. Additionally, loose installation bolts on the clutch assembly, along with rust or corrosion, can exacerbate the vibration. During routine inspections, it's common to find oily stains on friction materials or peeling anti-rust coatings. Improper clutch pedal positioning during semi-engagement or aggressive throttle application can worsen the vibration. To resolve this, a comprehensive inspection of the clutch components is necessary, potentially requiring replacement of the clutch kit or resurfacing the flywheel. Don't forget to check for aging or cracking in the engine mounts, especially crucial for vehicles over ten years old. DIY checks can include listening for unusual noises from the clutch pedal, but professional repair is recommended to avoid driving safety hazards.
