Metzeler ME77 Rear tyre 120/90/H16 (GPZ 500S A1-A6)
Correct tyre sizes for A1-A6 machines are

100/90/H16 Front, and 120/90/H16 Rear.

Correct tyre sizes for D1-> machines are 110/70/H17 and 130/70/H17 Rear.

It is illegal to mix:-
Bias belted front with Crossply rear
Radial front with Crossply rear
Radial Front with Bias belted rear