Product: Motorized Bicycle Chain Tensioner (adjustable for 49 cc, 66 cc, 80 cc engines) Key benefits — why you need it Keeps correct chain tension and alignment to extend chain life and prevent derailment. Less slack means fewer dropped chains and smoother power transfer. Reduces sprocket wear by maintaining consistent alignment, saving money on replacements and maintenance. Increases riding safety and reliability by preventing chain jump and breakage during acceleration or rough terrain. What it does (function) Adjustable chain tensioner that secures proper chain tension and alignment for motorized bicycles. Designed to fit and work with 49 cc, 66 cc and 80 cc motor-electric engines. Compatible with both mid (middle) and rear drive setups on motorized bicycles. Key attributes Compatibility: Fits motorized bicycles with chain drive using 49 cc, 66 cc or 80 cc engines; suitable for mid and rear drive mounting. Adjustability: Fine-tune chain tension for an optimal fit and consistent performance across multiple engine sizes. Material & durability: Constructed from high-quality materials for long service life; resists deformation and helps prevent chain jumping and breakage. Performance: Provides consistent tension under load, improving drivetrain efficiency and reducing noise and wear. Practical applications / use scenarios Converting or upgrading a bicycle with a 66 cc engine: Install the tensioner to maintain correct chain alignment during city commuting and avoid frequent chain drops. Off-road or hill riding with an 80 cc setup: Use the adjustable tensioner to prevent chain derailment under heavy torque and rough terrain. Lightweight motorized commuting with a 49 cc engine: Keeps the drivetrain smooth and quiet for daily rides, reducing maintenance intervals. Simple benefits for the user Less maintenance: Fewer chain adjustments and sprocket replacements. Safer rides: Lower risk of sudden chain failure or derailment. Better ride quality: Smoother power delivery and reduced drivetrain noise. Notes for buyers Verify compatibility with your motor position (mid or rear drive) and engine size (49 cc, 66 cc, 80 cc) before installation. Proper installation and adjustment are essential for optimal performance and safety. If unsure, consult a mechanic familiar with motorized bicycle drivetrains.