I feel I should put a post about the bikes (and luggage).
Let's start with my XT250. It is a 2009 grey import (to the UK) from Japan. It has probably bewn badly crashed over there and has few issues with the electrics, but nothing major.
Modifications / preparation:
1 / Tubeless back wheel (and front wheel): fitted with heavy duty inner tube and filled with "green Slime". It seems to have done the trick as both during my 2016 trip and this trip I had zero punctures.
Fitted with Shinko tyre at the back in Kyrgyzstan in 2016. Not replaced as it was truck back to the UK.
Front tyre: Pirelli MT21.
2 / handle bars replaced by rental ones.
3 / full service, new sprockets, chain, fluids, K&N air filter, (new wheel bearings if I can remember?)
And that's about it.
Alistair's bike: Honda CRF 250
This one, we spent more money on it as it was its first overland trip.
In addition to the XT250 point 1 and 3:
1 / 12 litre fuel tank fitted
2 / custom made frame to fit our soft panniers, as well as fitting under the luggage frame a 5 litre fuel canister. (My XT250 has a 10 litres tank and I did not want to change that - I carry a 5 l fuel bladder instead for extra).
3/ Alistair fitted a small tool box on the tail, to be used as a top box, for tools and waterproof.
We also got a £20 horse riding gel saddle over the seat, about 2 inches thick, for comfort, identical to mine. They remain in place with just some elastic.
That is about it for the work done on the bikes.
How they look like:

Now, why do we travel with such small bikes? Only 250cc, I hear you ask!
First, I did the one year long trip (around South America ) on a BMW 650 GS. For me, it was a complete nightmare.
First, it broke down pretty much everywhere. Then it was way too heavy for me to handle, once we ran out of tarmac. So in the end there were lots of place we did not go as it was too hard for me to ride through that. At the time my only experience of dirt roads was the BMW weekend course in Wales. Not enough.
Then we rented 2 small YBR125 in Vietnam a couple of years later, for few weeks. For me, it was a revelation.
All of a sudden, all those terrifying rough tracks were actually fun to ride. So from there, we decided to downgrade.
No point in Alistair riding a 1200 something if I cannot keep up. It would cause a lot of trouble in our couple

.
I have seen enough couples, him on the big bike, her on the little one. Him pissed off because she is going so slow, her pissed off because she struggles to follow. Not good!
With our 250s, outside of the western world, we have enough speed, and they are light enough to go through anything. Also, they are very simple to repair. With my BMW, 10 years ago, finding someone with a computer to plug the beemer in the middle of nowhere in Bolivia or Patagonia was impossible, unless trucking it to the capital city.