The SX: From 1992 through 1995 single carb, non agressive hull, no longer ride plate, big rider protection on the handlepole.
The SXI: From 1995 through 1997 twin carb
The SXI Pro: From 1998 through 2002, new hull more agressive, longer ride plate,...
The SXR: From 2003 through 2011.