>Buy - ride - sell?
If you have a bit of time at the end of the trip then buy-ride-sell can be ok - BUT you need a quick sale so expect to offer the bike at a bargain price to get buyers quickly. There are a few formalities required when selling any motor vehicle - a safety certificate is required for anything over $1000. Being a federation the laws can be slightly different in each State as well.
>Hire one way?
Cant help you out there, but I doubt you'll find someone who can do that for you.
>Into Perth out from Sydney?
Where are you coming from? Perth is a smaller city and will be harder to sell a bike.
>Or the other way around?
>Looking to spend about 2 months doing it.
Not long enough, but then again I always say that.
>Two weeks ish at either end?
Maybe a week at the start to buy a bike and get settled in.
>Is a month long enough to get across?
Depends which way you go, South via Adelaide is an easy ride, good highways, in winter can being bloody freezing. North via Darwin the roads are worse, from Novemberish to late March it can be very wet due to monsoon season, roads can be cut.
>Best time of year?
Australia spans the tropical North to Alpine country in the South. Depends on what you want - summers can be hot and dangerous if you venture off the highways in 35C plus temps. Winter months in the north are usually dry (this year being an exception) with 25 to 30C days and 20C nights. Further South 10C nights and 20C days (Brisbane), Melburne -2C nights and anythjing from 5c to 10C days. Summer its just hot everywhere, it just depends if you like it dry hot or wet hot.
>4 - 5 hours riding a day?
>Looking at DR650 / XR400 sort of bike.
We have travelled throughout Australia on BMW R65s (1981 and 1979) and they are ideal bikes (IMHO) lightweight, great for outback touring, usually have panniers and racks, good mileage, simple mechanically. I've been up and down the Birdsville Track on one, and ridden through snow in Snowy Mtns.
>Best place to source one?
I'd buy from a dealer, you pay more, but they will also handle the registration paperwork, get you insurance etc. Third party injury insurance is compulsory and you pay that with the bike reg. Do an eBay search or www.tradingpost.com.au
to get some price ideas.
>Vehicle recovery - if it all goes wrong?
Your own country's motoring club may have a reciprocal recovery agreement with each of the motoring clubs here - RACQ, RACV, SAA, NRMA
>Mainly roads but the odd excursion into the bush would be nice.
Always let someone know where you are going and when you'll get back. Each year there are always a few people who head off into the outback and dont come back alive.
>Staying in B&B with the odd night or two camping.
Try pubs (hotels), B&Bs tend to be few and far between except in tourist areas. Most caravan parks also rent out onsite caravans, you only need the bedding. Motels are over priced for what you get. Pubs are great 'cos you'll meet the locals - maybe not at their best but you'll get a few ideas.