Years ago I crossed the Salar de Uyuni frequently in a small overland truck. Crossing from Uyuni to San Pedro de Atacama in Chile via San Juan (among other BFN villages. Stunning desert scenery. Used to overnight on Incahuasi Island on the salt (I believe there's a hotel there now - for the latest, talk to Chris and Suzie at Hotel Tonito in Uyuni, lovely people and great pizza!) Crossed the salt to Colca K then down to San Juan before crossing the Chiguana pan, where we usually spent a day having broken through the crust - no fun in a truck but a bike would be fine - while the soldiers at the checkpost on the other side watched through binoculars. Then on to Lagunas Colorado and Verde and eventually down the hill a vertical km or so to San Pedro and civilisation. Spent 3-4 days doing it. Fuel would be an issue on a bike - probably available in San Juan but maybe nowhere else.
A daytrip or 2 onto the salt NOT to be missed, but if you can sort the logistics to go further, the desert the other side is stunning too.
Safest way onto the salt from Uyuni was head W out of town towards Colchani and go left onto the pan approx S20deg18'7.8", W66deg56'7.7" (sorry for old fashioned coords, I was young and knew no better!)
Incahuasi Island 61km at 283degrees, I think coords were S20deg14'25.4", W67deg37'36.9"
Causeway leading onto dry land the other side, if you're crossing, started at S20deg34'34.3, W67deg32'54.3" Surrounding the causeway the "ground" is soft and you could lose a truck in it for 3 or 4 days. (Don't ask!)
I think the salt crossing was 90 or so km, but my memory is a bit vague. San Juan was 50ish on rough roads from the causeway. After that, I remember camping just after the checkpoint with the binoculars, if we hadn't been stuck somewhere! 1 daysworth from Incahuasi to there with plenty of photostops. Play in the desert around the Arbol de piedra if you've fuel. Also v cool place to overnight. After that, leave Oblivia near Laguna Verde and head downhill, where it'll feel like you only have to breathe once a minute!
Beautiful place. Hope this helps, but be wary of the accuracy of my old handwritten route notes.
Simon