From RepROM for an older 1200GS (I don't know if newer bikes have different handlebar clamps- but I doubt it!)
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Place clamping blocks (2) on the handlebars.
Position the handlebars complete with clamping blocks (2) on the fork bridge. The position of the handlebars is indicated by a punch mark (arrow) on the handlebars.
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Warning
Failure to tighten the fasteners of the handlebar clamping blocks in the correct sequence could enable the handlebars to work loose when the motorcycle is being ridden.
Tighten the fasteners of the handlebar clamping blocks to the specified torque and in the specified sequence.
Tightening torques
Steel handlebars to fork bridge
M8 x 30
1st front, 2nd rear -> gap only at rear (as viewed in forward direction of travel)
28 Nm
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This site
http://www.r1200gs.info/misc/torque.html says 21Nm.
Rich.