I suppose it is possible (anything is), but would you enjoy yourself ? How large a motorbike will you be riding ?

That depends on many things, like what you like and what you want to see, part of the journey is stopping at places that take your fancy but would not interest others.

It is a long route, you will get many ideas of people.

The one you can afford, and it is Chile so that may limit you on the cost factor.

Try and get a 400-650cc single (IMO), an old BMW or KLR would probably do the job, and treat it as a throw away item.

Up to you, crossing the gap with a bike costs money (and time), it depends on your budget, your time seems short. So maybe use the majority of it getting to Colombia and then try alternatives for the last leg home.
That is the $64,000 question :-)
First research the bike prices, and then start from there.
Are you camping or hosteling ?

Chile is cheap to wild camp, but not for any other sort of accom (IMO)

Peru is cheap for small town hostels.

FWI, my wife and I mixing and matching accommodation can still manage Chile/Arg/Bol on less than $100/day for two people and two bikes. So start with a $50/day budget.

Gas prices vary, and that along with food is where you will find a lot of cost.

You have started the research that is a good start. Now go and have a good read of the South America section :-) Just about all the questions you have asked, and the ones you haven't , will be listed there.

Have fun

Oh, and while in Chile, give Lorraine Chittock a shout, she is 2 hours north of Vina Del Mar and is always glad to see travellers and help out.

http://www.horizonsunlimited.com/hubb/members/lorraine

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