The carburetor size is an oval hole about 13x16 mm at the curb. Corresponds perhaps about a circular 14 mm but difficult to say exactly. Connection filter 35mm. Fits among other things Lifan 4-stroke with horizontal cylinder Main nozzle: 74. (Bing 4mm)
Carburetors, whether original or replica, need to be cleaned before installation.
Take the opportunity to get to know your new carburetor by disassembling it and making sure there are no metal shavings left over from the manufacturing process.