Give your compatible 139QMB scooter a bigger-displacement foundation for your next off-road build. This Universal Parts 47mm cylinder kit upgrades a matching 50cc four-stroke engine to 72cc and brings together the cylinder, piston, rings and installation gaskets in one convenient kit.
This product is intended for off-road use only. This product is not intended for use on public roads or land.
Features
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72cc upgrade: Increase displacement on compatible 139QMB-based 50cc four-stroke engines.
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Matched top-end components: Includes the cylinder, piston, rings, piston pin and circlips.
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Included gaskets: Head and base gaskets are supplied for the top-end installation.
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Finned cylinder: External cooling fins suit the air-cooled engine layout.
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Defined fit-check dimensions: A 47mm bore, 52.7mm sleeve outer diameter and 13mm wrist pin help you plan your build.
Specifications
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Brand: Universal Parts
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Part number: 151-255
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Engine application: Compatible 139QMB-based four-stroke engines
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Upgrade displacement: 72cc
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Cylinder bore: 47mm
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Cylinder sleeve outer diameter: 52.7mm
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Wrist pin diameter: 13mm
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Total piston height: 34.4mm
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Compression height: 17.25mm, measured from the wrist-pin hole center to the top edge of the piston
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Kit contents: Cylinder, piston, rings, piston pin, circlips, head gasket and base gasket
Model Fitment
For matching Chinese scooter 139QMB-based 50cc / 80cc engine applications using the following engine codes. This kit provides a 72cc configuration; verify existing components on previously modified engines.
| Engine Family |
Engine Codes / Applications |
| QMA / QMB |
139QMA, 139QMB, 1P39QMB, 1P39QMA-2, YN139QMB, JJ1P39QMB, BD1P39QMB, BN139QMB |
| Additional applications |
139FMA-2, 147QMD, other matching QMA and QMB models |
Installation note: You may need to modify your engine case to accommodate the cylinder's 52.7mm sleeve outer diameter.
Check the engine code stamped on your scooter before ordering. Engines marked with a listed code may use this kit, but verify sleeve clearance, wrist-pin diameter and piston dimensions against your engine. A code containing “QM” or “FM” alone is not enough to confirm fitment.
