You must STOP, press and hold the ABS button till the brake light glows red and then continue. There's no need to turn the engine off. When you want to re-activate it, you must stop, press the button again and go.
The ABS wheel sensors must not be sensing a rotating wheel in order for this to work, that's why you must stop. I have never seen any bike with switchable ABS where you can turn it off while the bike is in motion as a factory setting. On the SuperTenere 1200 since it does not have an ABS switch, someone made one, so you can turn it off at any time.
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