Completely Assembled PAIR Style Cylinder Head for 50cc 4-stroke QMB139 engines.
PAIR is an acronym for Pulsed Secondary Air Injection System. It is an emissions control system used to lower HC and CO emissions. It works by allowing air into the exhaust flow.
 
Intake Port Diameter: 17mm
Exhaust Port Diameter: 17mm
Valve Length: 69mm 
Emission Control System: Pulsed Secondary Air Injection System(PAIR)
 
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