Naraku 90cc Cylinder Kit V.2 with cylinder head for GY6, 139QMB, Kymco 50 2V

Description

QMB139 Naraku High-Performance Parts - 90cc Cylinder Kit Naraku V.2 with cylinder head for GY6, 139QMB, Kymco 50 2V
With the latest V.2 Cylinder kit series from NARAKU, we can offer a more advanced product. The bore has been taken out to 52.4mm. The external diameter of the cylinder base has not been affected by the increase in displacement. This means alterations to the crank cases are generally not required. As a 4 stroke cylinder is effectively just a hole, the emphasis on technological development was placed on the piston and compression.
Specs:
Cylinder Bore: 52.4mm
Cylinder Sleeve Outer Diameter: 54.4mm
Wrist Pin Diameter: 13mm
Total Piston Height: 36.3mm
Compression Height (from center of wrist pin hole to top edge of piston): 20mm
Intake valve: 23mm
Exhaust valve: 20mm
Intake Port Diameter: 20.8mm
Exhaust Port Diameter: 18.7mm
Uses Short 64mm Valve Stems
The piston has 2 additional CNC-machined oil grooves in the piston skirt, which collects engine oil to lubricate the cylinder bore and improve characteristics in extreme circumstances. The molybdenum coating aids the crucial running-in period. 2 oil recesses and a groove at each bearing point ensure the gudgeon pin is adequately lubricated. The compression ratio and power delivery set this cylinder apart. The kit contains a cylinder head with larger valves and optimised inlet and outlet ports. For technical reasons, a bore size of 50mm or larger requires a larger head for on-going use. This kit is currently one of the biggest conversions on the market. The kit can use the original carburettor, but we recommend changing the main jet.
Please note: For Sym scooters this kit is only suitable for the GY6 139QMB engine version and not the XS1P139QMB, AV05W or AW05W engine or the Sym Symply 2 models
About Naraku Scooter Parts
Naraku is one of the best known scooter brands from Taiwan. The company has made a name for itself when it comes to after-market racing scooter products and professional replacement engine parts. As our in-house performance brand we carry the full range of performance products. When selecting Naraku or any major performance brand we suggest not to mix and match brands know that Naraku components are designed to work with other Naraku components for the best performance possibilities. Keeping your racing upgrades in the same brand makes it easier to tune since they are designed to work with each other. Naraku is one of our top tier brands with our highest recommendation.