@s dont die easily. But if you're determined to abandon it, then you could weld the sprocket onto the shaft. It'll take maybe 5 minutes. Use a new sprocket. It can later be cut off with an angle grinder so thats not a problem. Its impossible to say how long it will last as it is from your description. But the stresses of African roads may be too much. Personally I would fix the bike by myself for cost reasons - or weld on the sprocket to the shaft. You must disconnect both batt. terminals or risk frying your wiring system. You should also remove the tank.

You dont say how many miles it has done. I bought one at 60k, its now at 100 k (miles) and just fine.

If the oil leak is from the g/box bearing (you dont say where) then it can collapse any time - you might make it - you might not. No-one knows that. Somebody above said that too - I agree. My nerves couldnt stand that uncertainty! You could easily live with the oil loss at that rate, but its the bearing which is the issue. Unfortunately, that bearing requires a whole engine and gearbox stripdown, like the shaft. BTW, the shaft costs about £100. Gaskets cost about £50-ish I think.

One bloke in Southern Spain has asked for your bike as a freebie. Why not get him to offer you some money (say £300-£400) to help you fix it up, and then deliver it to him after the trip - fair exchange, and everyone happy.

Dont dump it -I bet you it's not so bad. But if you're up for jumping on a bus if it dies - then I say weld it, chance it, drive gently. Carry 5 litres of oil, even used oil. You might make it.....but leaving a bike like that? oooh that hurts!

But then you could sell it to the punter in Spain if it gets back - now that would be a happy ending for all!

Good luck - tell us how you get on - what you did - and how the bike lasted. (the output shaft on both my @'s wore out...I intend redirecting some of my chainoiler feed onto that shaft).