The fork legs are slightly different. Axle bolt sits at the bottom of the leg on an X model,slightly up and in front of the fork leg on the R for more travel and bigger wheel clearance.
Later X models came with newer (smaller) side panels and revised tail plastic and lamp area, plus alloy swingarm which the R never got.

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2011 xt660z.
Yoshimura cans ,kev mod,Dna 2, Stahlkoffer panniers,Hepco Becker box,Givi crash bars,Mita e07 tyres.