Cylinder Piston Kit 59mm Big Bore Replacement for Yamaha Mio/Sporty/Smile 113cc

  

Complete kit: cylinder, piston, rings, pin, circlips, and gaskets. Replacement unit - bolts on directly; verify the pin diameter before ordering.

Aftermarket - fuel adjustment may be needed after installation. Overview This 59mm cylinder piston kit is a top-end replacement option for Yamaha 115cc and 125cc air-cooled 4-stroke engines. The kit increases displacement from the standard 53.7mm bore to 59mm, providing a noticeable increase in torque and power across the rev range. The kit includes the cylinder, piston, rings, pin, circlips, and gaskets - all parts needed for a complete top-end rebuild. Replacing worn parts with this kit can help restore performance and add extra power. Mio / Mio Sporty / Mio S. Mio Smile / Mio Soul i / Mio Gravis. X-City 115 / X-City 125. Note: This table is for reference only. This kit is for engines with a 59mm bore and typically 14mm piston pin - verify your existing piston pin diameter before ordering. Always confirm your engine code and bore size before purchasing. 59mm bore - increases displacement for improved power and torque. Complete top-end kit - includes cylinder, piston, piston rings, wrist pin, circlips, and gaskets. Aluminum cylinder - lightweight with good heat dissipation. Helps restore compression and power - replacing a worn cylinder can help reduce blow-by and restore throttle response. Replacement unit - uses existing mounting points - no modification is needed in most cases. Drain engine oil, remove the old cylinder head and cylinder. Clean the mating surfaces thoroughly. Install new rings onto the piston - stagger ring gaps as per the service manual.

Lubricate the piston, rings, and cylinder bore with clean engine oil. Install the piston with the arrow facing the correct direction - secure with new circlips. Install the new cylinder over the piston using a ring compressor. Reinstall the cylinder head - tighten fasteners to the specified torque.

Refill with fresh engine oil and follow the proper break-in procedure. This is an aftermarket replacement product - it is not associated with Yamaha. This kit increases displacement - it is not a standard replacement.

Piston pin diameter - verify your existing piston pin diameter (typically 14mm) before ordering. Fuel adjustment - after installation, you may need to adjust the carburetor or fuel mapping. If issues persist after installation, inspect the cylinder bore and valve train. Always use a torque wrench when reassembling cylinder head and cylinder fasteners. Condition: Brand New - Aftermarket Replacement.