I got tired of all that ABS button crap pretty quick.
I wired a ON/OFF rocker switch into the rear brake ABS sensor circuit. When switched off this basically causes the ABS to fault and turn off.
Now when off road I flip the switch to the OFF position the ABS stays off until I want it on again. No need to touch the factory ABS switch.
All it cost me was:
1) On/Off rocker switch
2) 2 male / 4 female wire connectors
3) about 8 feet/2.5 meters 16 ga. wire
4) 1 hour of my time
I had all this stuff lying around so it was free for me, might cost $10-$15 if you had to buy it.
The first step is to follow the glossy black wire from the rear ABS sensor pickup, you will find it ends under the seat above the rear shock.
I stripped about 40-50mm of the insulating cover off the wire leading into the female side of the connector. I cut one (doesn't matter which one ) of the wires and added wire connectors and then ran two wires along the frame rails to my switch on the dash.
When the switch is flipped OFF the signal from the rear ABS sensor is interrupted causing the system to detect a fault and turn off.
Here is a picture of the factory connector under the seat and my "splice" into it. The black stuff you see on my connectors is "liquid tape" for some additional water proofing. ( sorry, the pic could be be better, but you get the idea )
Here is a pic of the dash switch. I got this switch from Radio Shack for $3.
To turn the ABS back on just flip the switch back to ON and restart the bike.
You could also tap into the front ABS sensor and accomplish the same thing ( speedo/odo won't work though ).