Tyres

I did carry my TKC80s down through France and Spain to Morocco and then back home again. The pair are very heavy (15kg?) plus the homemade carrier.

Whilst you may not be able to buy TKC80s you should be able to buy some sort of knobblies in big towns. At least, other people seem to be able to buy them so you now know you need to up your game if you seemingly can't.

That said, I've wussed out and bought a spare TKC80 rear for India. I've read that it'll be virtually impossible to buy 17" rear tyres (or 21" fronts) after Istanbul. The downside of travelling on TKC80 (ie. knobbly) tyres is that they wear rather more quickly than many road tyres. I may find myself halfway through with bald tyres. I might need to find a vulcaniser!

Inner tubes

(if required). You should try to replace your normal inner tubes with heavy duty ones which will cut down the risk of a puncture proportionally. However, 4 inch nails are four inch nails and no respectors of 4mm inner tubes. Pack a spare.

My spare is actually the original inner tube. I'm feeling lucky.

One slight oddity, here. No-one seems to make a 4mm heavy duty inner tube for 17 inch tyres (ie. for the XT's rear). That's very annoying. The 17 inch rear seems to be a bit anomalous in general. If you can get a bike with an 18 inch rear, all the better for you.

Puncture Repair Kit

Not technically a spare, per se, (although I do have two) you will be using it to mend your inner tubes. In fact, my only use of it has been when I was practising changing tyres and pinched the tube...

Spark Plug

I've opted for an Iridium spark plug so, technically, the original is the spare and the iridium plug is in the bike. The benefits of iridium are techno burble which will hopefully result in better fuel efficiency.

Oil Filter

At some point I'll have to pay someone to do some sort of mechanical stuff with the bike and you can bet they won't have a oil filter for a medium selling Japanese dual sport bike. Best take one with me to save some hassle.

Brake Pads

I don't remember my brake pads having been changed in the 19,000 miles I've had the bike -- you can bet I haven't done it. The forums have wildly varying lifetimes for brake pads from 1500 miles (which I think is people riding the back brake when off road) through to 30,000 miles which is more my kind of figure. Whatever the value you can bet there'll be some metal on metal action someway along this trip and they won't have the right parts.

Bulbs

Technically a requirement in many parts of Europe.

Bungees

A bit of an odd one, but bungees break just like anything else especially if they're put under stress by you crashing through potholes in rough tracks.

Chaindrive

I've wondered about carrying a whole spare chain and sprocket set but they weigh a ton and when was the last time one failed on you?

OK, mine failed on me due to neglect and my mate phoned me the other day as his had failed due to neglect/overuse. But, you know, in general, how often do they fail?

That said, the "how often do they fail?" argument is bogus. You will, by definition, be doing five years worth of riding in a few months. So, how often do chains/sprockets fail in five years of heavy use?

Bah! You can start getting a bit anal! Keep an eye on things and head to the nearest big town when things look serious.

Levers

If your levers break then you don't have the physical oomph to pull on the levers' remaining stumps. You should carry spares.

Except, I go for the metal-in-the-handguards argument which should mitigate this problem.