Hello Terry,
from uyuni there are more or less to route going to chile/san pedro de atacama.
1. ollague
the option to ollague is the easy road. the road to san cristobal is for bolivia in quite good condition. but take always the main roads, there is a shortcut which won´t be nice for your bike
the begining should be paved now.
After the border you have mostly a paved good road. only if they work on it you need to go over gravel. the road goes around the smokey volcano too some lagoons. it is nice.
You will arrive in calama and head to the left to San Pedro de Atacama.
You need two or three days for this route it depense on skills.
2. Nationalpark
I would always recomend this route. The landscape is just amazing. It is more ruff, so it is harder for your bike and for yourself but it is worth it.
You take also the route to San Cristobal. Tank gas there! But later you will leave that road and drive to Vila Mar. (Before vila mar are some stone formations on the right side you can visit and take some snapshots) In Vila Mar you can stop and rest or you go on. The next possibility is in the Nationalpark.
It goes through a valley up in the nationalpark eduardo avaroa (150 BS)
This part is not that difficult.
The difficult road starts at the first lagoon -Laguna Colorada. It will be sandy and there are deep tracks. You go arounf the red lagoon, on the right side in the south is a hostel. You can find it easily. If it is late you should stop there and rest. It will be full of 4x4 trucks and tourists from uyuni. From there you go to south leaving the lagoon, riding up a gravel road. You need to come to a street which goes from the thermal springs along the geysers to a border control. This part is heavy. so many rocks on the way, but there for it it isn´t sandy. Just take care of your tyres. there are hundreds of tracks...just choose one.
on the better road you take a right to the border. There are two more controls but the aduana at the nationalpark border isn´t open so often. so go to this one and check out your bike! Afterwards you go all the way back, where you took a right and you go further straight on your road. This road is easy and good driving for gravel. on the right side is a big geyser field. visit it, it is muddy cool.
you go down to the next lagoon to a little village with hostels and also a thermal pool. if you did not rest at laguna colorada here is a good possibility.
Just follow the road and after a while you come to laguna verde. a green lagoon in front of a volcano. it is amazing! you can go around to the left or right, it think the left site is more easy and you have a nice view with the lagoon and the volcano. of course there are also a lot of flamingos, the most time. on the south west end there is the nationalpark control and sometimes the aduana for a second time. You check out of the nationalpark and tell the aduana guy that you went to the otherone. if he will work^^. 5km further is the border to chile. There is your check out of bilivia.
You will come to pass jamal. at the moment chile builds a border control on top. maybe it is finished till your trip. otherwise your check in point is at the begining of san pedro de atacama.
if you need help, there will be plenty of tourst groups in 4x4 on this way. so don´t worry. I don´t know your bike but maybe take a spare tank with you. You need gas from vila mar to san pedro de atacama.
The way from uyuni - nationalpark eduardo avaroa - san pedro de atacama will take three days.
Questions?
best wishes from brasil
Sascha