And there you have it. If you have a new one you can now install it.
If you don't have a new one you can try to fix this one by removing these four screws and removing any blockage.
Now Keurig doesn't stock spare parts, so unless you can get your hands on another broken machine you will need to fix the existing motor or source a new one. Radio Shack stocks small motors like this, they won't be exact but with a little modification you should be able to get it working.