Helchuan is found patrolling a route in Länsi-mâ in Forochel, north of Zigilgund and east of the hot springs, walking in a loop between [11.0N, 81.7W] and [11.0N, 80.8W] (the "northern loop", shown in the image below).
The southern loop is only used once, when he spawns there, after a roundabout near the 7th Dwarf Channel he sticks to the northern loop. If he spawns in the northern loop he sticks there. Helchuan probably won't spawn if there is the Great Hoary Aurochs in the area - also level 50 signature standing in about the middle of the northern loop.