Hello skrichter,

The O.S Carburetor in each engine model are as follow,

21XZ-B Spec I - Type 21J2(B) - 2010
19XZ-B - Type21J2(B) AR6.0 - 2011
21XZ-B Spec II - Type 21J(B) - 2013
B2101 - Type 21J(B) R6.0 - 2014
21XZ-B Spec III - Type 21J3(B) R6.5 - 2016
B2102 - Type 22C(B) R6.0 - 2016
B21AD - Type 21J3(B) - 2017

21XZ-B Spec I and 19XZ-B has Short Metering Needle (Low Mixture Needle)

The above Carburetor are the only two that has Short Metering Needle (Both with same Needle Part Number). 21XZ-B Spec I comes with 6.5mm Venturi while 19XZ-B comes with 6mm Venturi.

XZ-B Spec II and B2101 have the same Carbutetor, the only difference is the Venturi type. The B2101 has the newer type Venturi.

XZ-B Spec III and Adam Drake have the same Carburetor, the only difference is also the Venturi.

The above four Carburetors are actually the same, the only difference is the Thermal insulator design. The 21J3 Body has the newer Black Insulator without the additional lower thin ring.

B2102 Carburetor is the different between the rest.

Hope this is clear enough..

Cheers..