Catching Chimecho is hard-It took hours for most people.
But, I have to say that it's NOT impossible to get a Chimecho.  Here's a somewhat "Guide" to catch Chimecho.

1. Fly to Lilicove. Use a Max Repel, then Go to Mt. Pyre.
2. There are 2 parts in Mount Pyre-The Part where you can't use your Bike and a Part where you can. Go to the Part where you CAN use your Bike.
3. Go up until you see a Fog. Then go to the next part-Where every part you see is Fog.
4. Go up until you see the old couple-The ones in charge of the 2 orbs.
5. After this, Go north aiming at the old man until you can't move anymore. Then, take 5 steps Down, face left, and go to the thin Slot you're facing at.
6. Head there until you see a pile of Grass. That's Chimecho's Territory.

Note:Chimecho is a very rare Pokemon, but it is NOT legendary, which means you can catch it as many times as you want.

If you really like to have more Chimechos, catch a Male and a Female one, and place them both in the Daycare. Get the eggs from the Old Man, and hatch them. I've gotten quite a number of Chimecho's because of this ;)

Chimecho's Pokedex Info:
#151 Chimecho
Wind Chime Pokemon
Height [x] 2' 00"
Weight [x] 2.2 lbs.
About:
In high winds, Chimecho cries as it hangs from a Tree branch or the eaves of a building using a suction cup on its head. This pokemon plucks berries with its long tail and eats them.

Area: Route 122, Mt. Pyre

I'm quite a Chimecho Fan myself =3 Mail me if you have any questions^^