There is a 43, 49cc Zen/Mitsu piston port engines, and Cag reed port engines, a 47cc is really 43cc, and the 49cc is 48.7cc. Both engines use the same 40mm & 44mm piston and rings, pin and 10mm bearing. The 49cc Cag has a 12mm crank unless it is a 47cc that has a 49cc Big Bore kit.
All the other parts are different. First photo is a piston port, the second is reed port.
The 39cc reed engine was /is often referred to as a 47cc engine. 43cc is a piston port. To make it confusing there are 49cc reed and piston port engines. Reed engines on pocket bikes typically use slide carburetors (throttle cable points straight up out of the top of the carburetor) and piston port mid bikes come with a barrel valve type carburetor (cable attaches to the carburetor from the side).
That's the way I under stand it. The Cag 47 is almost 40cc, and the Cag 49 is 48.7cc. The piston port comes in 43 and 49cc, which uses the same 40 and 44mm piston, 10mm pin, with the arrow always facing the exhaust port. On the 49cc Cag factory engines the piston pin is 12mm.