To unlock the medium kart called B-Dasher, you have to unlock all twenty-four expert staff ghost data entries. Below are the times needed to unlock them.

Bowser's Castle | 03:04.836 | 02.55.017 | 02.42.098
Coconut Mall | 02:30.764 | 02.24.788 | 02.13.333
Daisy Circuit | 01:56.822 | 01.48.791 | 01.41.362
DK's Snowboard Cross | 02:34.693 | 02.24.725 | 02.17.546
Dry Dry Ruins | 02:30.949 | 02.21.681 | 02.14.286
DS Delfino Square | 02:41.807 | 02.33.107 | 02.24.169
DS Desert Hills | 02:10.233 | 02.01.141 | 01.52.686
DS Peach Gardens | 02:34.894 | 02.29.006 | 02.16.777
DS Yoshi Falls | 01:16.461 | 01.12.901 | 01.09.175
GBA Bowser Castle 3 | 02:58.304 | 02.50.637 | 02.39.391
GBA Shy Guy Beach | 01:45.568 | 01.39.255 | 01.32.867
GCN DK Mountain | 02:57.744 | 02.50.248 | 02.38.130
GCN Mario Circuit | 01:59.771 | 01.55.267 | 01.49.939
GCN Peach Beach | 01:34.233 | 01.30.698 | 01.23.140
GCN Waluigi Stadium | 02:32.882 | 02.24.645 | 02.12.367
Grumble Volcano | 02:28.237 | 02.19.524 | 02.11.852
Koopa Cape | 03:03.022 | 02.54.897 | 02.41.370
Luigi Circuit | 01:29.670 | 01:24.957 | 01:19.419
Maple Treeway | 02:58.633 | 02.50.229 | 02.37.812
Mario Circuit | 01:44.777 | 01.39.183 | 01.33.702
Moo Moo Meadows | 01:37.856 | 01.33.571 | 01.25.909
Moonview Highway | 02:16.802 | 02.07.016 | 02.04.163
Mushroom Gorge | 02:16.110 | 02.05.494 | 02.01.011
N64 Bowser's Castle | 03:19.323 | 03.06.723 | 02.55.933
N64 DK's Jungle Parkway | 02:58.264 | 02.49.028 | 02.37.782
N64 Mario Raceway | 02:14.799 | 02.07.915 | 01.59.053
N64 Sherbet Land | 02:48.651 | 02.37.784 | 02.28.356
Rainbow Road | 03:05.895 | 02.59.293 | 02.44.734
SNES Ghost Valley 2 | 01:06.595 | 01.03.752 | 00.58.907
SNES Mario Circuit 3 | 01:38.880 | 01.34.828 | 01.26.659
Toad's Factory | 02:22.480 | 02.12.784 | 02.05.593
Wario's Gold Mine | 02:19.583 | 02.14.932 | 02.04.800