I just bought a new 2186, and neither bending the lever or unplugging a wire will work on it. Apparently they've changed things to make it harder to disable.
There's a lever linked to the reserve pedal that depresses a switch when the reserve pedal is pressed. It's under the frame, inside the left hand frame member. The lever is heavy metal and not bendable. You can see it from the right side if you put the deck all the way down and lay on the ground. However, nothing is easily accessible, including the wiring which apparently is run into the frame and then the steering column.
When my dealer delivered it, he told me the easiest way is to remove the lever--that means removing the deck and possibly jacking the whole thing up to get enough room to work. He said the switch is normally in the closed position (PTO running), so that if you unplug it, you also have to tap the leads together (or ground one?). It looks like you'd have to take apart the steering column to get at the wiring--not sure how you get to switch itself--and figure out which ones go to the switch.
Now the interesting part. Mine mows in reverse as I got it /forums/images/graemlins/ooo.gif I don't know if my dealer did it--I made a point to the saleman that I would disable it first thing (but not the owner that delivered it), and they had it for a week while I was on vacation. Or it could have been done by the dealer they got it from (they didn't have one themselves). In any case, I was happy! I haven't pulled apart the steering console to see how it was done, but it's obviously in the wiring since the lever/switch mechanism is still in place.
John