Give your GY6 build more muscle with the Naraku 63 mm Forged Piston 180cc Big Bore Kit. Designed for compatible GY6 125cc and 150cc four-stroke starting engines, this kit increases displacement to approximately 180cc for a stronger foundation for torque and acceleration tuning. A finned cylinder, forged piston, piston rings, wrist pin, retaining clips and gaskets bring the core components together for your big-bore upgrade.
Crankcase modifications are required to install this cylinder kit. This is not a drop-in replacement. See the NCY Engine Case Boring Tool to get the job done.
Features
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63 mm Big Bore: Increases displacement to approximately 180cc with the appropriate crankshaft stroke.
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Forged Piston: Performance piston supplied with rings, wrist pin and retaining clips.
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Finned Cylinder: External cooling fins help dissipate heat from the air-cooled engine.
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Included Gaskets: Cylinder head and base gaskets, along with additional sealing pieces, support assembly.
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Fitment Measurements: 64.9 mm outer sleeve diameter and 54 × 54 mm cylinder-stud spacing help identify the required engine configuration.
Specifications
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Brand: Naraku
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Part number: 137-11
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Engine application: Compatible GY6 125cc / 150cc four-stroke starting engines; excludes QMK and 169cc engines
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Bore: 63 mm
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Resulting displacement: Approximately 180cc, depending on crankshaft stroke
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Outer sleeve diameter: 64.9 mm
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Overall cylinder height: 90 mm
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Wrist pin: 15 mm diameter × 48 mm length
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Cylinder-stud spacing: 54 × 54 mm center-to-center; approximately 76 mm diagonal
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Additional mounting dimensions: 63 mm across the lower holes; 41 mm between the right-side middle and lower holes
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Installation requirement: Crankcase modifications required
Model Fitment
For compatible 125cc and 150cc starting engines only. Not compatible with QMK engines or 169cc starting engines.
| Engine family / codes |
Fitment requirements |
| 157QMJ, 152QMI, YN1P57QMJ, JJ157QMJ, 1P57QMJ, BN157QMJ, 1P52FMI, 154FMI and other compatible QMI/QMJ configurations |
125cc / 150cc GY6-A engines only. Confirm 54 × 54 mm cylinder-stud spacing, 15 mm wrist pin, cylinder height and crankcase clearance. |
Having “QM” or “FM” in the engine code does not automatically make an engine compatible. Match the mounting pattern, sleeve diameter, cylinder height and wrist-pin size, and confirm compatibility with your cylinder head and crankshaft. Plan for crankcase modifications and appropriate fuel-system tuning as part of the installation.
This product is intended for off-road use only. This product is not intended for use on public roads or land.
