slow time machine mavericks

Anyone with a solution?

Not me. But I wonder if maybe you're just up against the limits of the Time Capsule and its ability to integrate the presumably huge number of new Mavericks files into your existing backup. Could take a while, I would think, especially over the air.

In the absence of any other responses on this forum, you might look over in the Mavericks area, where this topic is much discussed — see, for instance, this thread:

https://discussions.apple.com/thread/5471457

Same issue here, hung up preparing backup. As suggested elsewhere, click on the hour glass (Spotlight) at the extreme top right of screen and see if it is still indexing. If so, let it finish doing so - could take hours. In my case it was only indexing an 8 gig flashdrive. As soon as I ejected the flash drive, indexing of course stopped, and timemachine started backing up. All seems to be well.