Bicycle Mechanics - Help choosing a replacement rear derailleur

My daughther's bike is a 21 speed mountain bike I purchased from wal-mart a few years ago. The rear derailleur was mangled by a neighbor taking out his frustrations. Anyway, I now need to replace it and no longer have the one that was removed. Here's what information I have

Shifters are on the handle bars and are the ones that click (indexing?) and the word Falcon appears on them.

Rear sprokets have following number or teeth
14-16-19-20-22-24-28

I called the local bike shop and they quoted $50 minimum for any derailleur they carry + labor and I only paid $80 for the bike. If it's going to run me that much, I'd just as soon replace the bike. Any advice on a supplier is helpful also.

Thanks,
edchest

I replaced my rear derailleur on a bike from toys r us, bought about 9 years ago. Apparently, the rear derailleur isn't the same as what they have now, in that the bike frame does not have a derailleur hanger built in. I had to get a derailleur with the hanger built into the derailleur.

http://www.jensonusa.com/store/imgWrapper.aspx?img=/rd/RD407A06__________2.jpg&type=2
http://www.jensonusa.com/store/imgWrapper.aspx?img=/rd/RD406A03BKS.jpg&type=2

If you notice the top left of each pic, you'll see the difference. My older Toys R Us 21 speed mountain bike needed the derailleur with the built in hanger like in the second pic. $13 +s/h. Cheap, but works fine for what I needed it for.

I believe from what I've read that those are Shimano Tourney knock-offs, and so are Shimano compatible. If so, look for a Shimano Tourney or Alivio derailleur, long cage. An 8 speed der will work fine on your 7 speed bike.

Like this: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110146139519

Also, make sure that the derailleur hanger (holder) didn't also get snapped off the bike when the derailleur did. If so, you may be completely out of luck, because I doubt you will be able to find one for a $80 bike try derailleurhanger.com). This page shows you an image of a typical hanger and how to straighten it. Keep in mind if it's aluminum and bent, it might snap when you try to straighten it.

http://www.parktool.com/repair/readhowto.asp?id=39

Best o luck.

Another option is to check the local Goodwill etc. for a donor bike. Remove what you need and "donate" the bike back.
As far as compatibility, I don't consider Falcon to be compatible with itself.:)

I believe from what I've read that those are Shimano Tourney knock-offs, and so are Shimano compatible. If so, look for a Shimano Tourney or Alivio derailleur, long cage.
I have a used Tourney with built-in hanger if you determine that's what you need.

Thanks to all for your help. I ordered an inexpensive Tourney and installed it, only to find that the front sprokets (on the crank) are warped/out of plane and the chain slips off one and onto the next as it spins. I just can't win here. I'll need to fingure out whether that repair is worth the $ and effort.

Thanks again

can you get an adjustable wrench on the front chain rings and straighten them?

I got a SRAM 3.0 ($20 on Amazon) and it works well... That was for my walmart bike that is now destroyed.

Also, it's not worth a repair, honestly. Cheaper to spend money on a new bike. You're going to find another problem when you fix the chainrings.