GY6 139QMB 50cc 80cc Scooter/ ATV Quad Bike Engine Chinese CVT engine Starter Motor
Commonly found in the below models
 
Elite 50
Sunny 50 
NZ 50 
Forza 50 
 
You should be able to find 139QMB stamped on the back of the engine near the rear wheel.
Pretty much all 50cc four stroke Chinese mopeds use this engine and this starter motor. 
 
Specifications:
Material: Copper
Dimensions: 11cm x 75cm
Weight: 650g
 
Features:
Premium Quality: Our starter motors are crafted to the highest standards, guaranteeing long-term reliability. You can trust in their durability, eliminating the need for frequent replacements.
Vehicle-Specific Design: Tailored to your vehicle's unique power requirements, our starter motors are designed for easy installation and immediate use.
Durable Armatures: The new armatures are precision-manufactured and undergo rigorous testing, ensuring an extended service life.
Easy Replacement: Replacing your existing starter motor is a straightforward process, allowing you to get back on the road quickly.
 
Please be aware that the actual product may vary in appearance from the sample image provided.