Well you have to tell us which '86 ATC you are putting the light on. I have an '85 250r housing on my 350x, it required no cutting of the harness but I had to make my own sub harness to go into the single bulb. If you want to put the X light on another trike I would say don't do it, the wiring is easy but the bulbs that the X uses are more costly and harder to find than the R's bulb. You can go to any auto parts store and get a 9003 type bulb and plug it right into the R's housing.
John
1985 Eddie Sanders ATC330r
1986 Monstecate
1984 ATC70 (awaiting 125cc transplant)
1984 ATC125M
1986 GSXR 750 - Keepin' it old school!
1999 Arctic Cat 500 4x4 plow machine
1999 Arctic Cat Thundercat 1000 (lake lizard)
1996 Arctic Cat Jag 440 L/C (ditch banger)