If youre located in parts of the world where the carburated bikes you mention such as Suzuki Dr650 or Kawasaki Klr 650 are available both will be good alternatives. The Dr650 will need more upgrades but are much lighter than the Klr, thats worth considering. Carburated bikes will struggle more in altitudes though.

Edit: The new KLR now comes as EFI from 2021.

Crf450L? Did you check the service intervals on that one? Oil change every 1000 kms and valve check every 3000 kms. Forget it mate, you are planning the adventure of your life, not let it be ruined by spending time or money servicing the bike every other day.

Some guys have already «adventurized» the KTM 500 - and get good results(?) I still havent understood how often oil change and valve jobs are required on such «adventurized» bikes, but I hope its not as often as standard.

Tenere 660 - I have taken one rtw, 200 k kms, too heavy and to unreliable. Not recommended!

If you can live with 27-28 HP I tend too agree with the last poster - the CRF300 RALLY will be all you need. Lightweight, reliable, economic, ok range (not great) not great on highways but will do 100 km/h, but not much faster. Will need better suspension, handlebars and hand protectors, bash plate and a few minor things more. But then again - most bikes will need some improvement.

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In the end everything will be fine. If its not fine its not the end....