...we are being asked this question very often. And we are always happy to reply: Nothing major!
It's been almost 40 000 kilometers since we left home. I rode off on my F650GS which, according to the documents, was first registered in 2010, but according to VIN info, it was "born" in 2008 and at that time had a bit over 20 000 km on it. While Linas got his brand new F800GS Adventure a month before the start and had only 1200 km at the time we left.
So here's a short overview of things that required attention at some point and the solutions we applied to it:
Asta's bike (2010 BMW F650GS):
On 34 000 km (the total mileage of the bike) the fuel pump died in the mountains of Argentina. We replaced it with Argentinean brand pump, we found locally in the car parts shop for about 50 euros. We easily replaced the pump in the backyard of the apartment we stayed in and the new pump successfully does its' job for over 20 000 km since then.
On about 40 000 km rear shock absorber became obviously too soft as the rear wheel started touching the plastics above it on some bumps. We checked the shock and found that the problem was in the spring as the rest of the shock worked fine. Local mechanic compressed the spring additionally by adding an extra thread. This not only solved the problem, but also made the bike taller... due to that, the bike was 'laid down' a few times more that usual while Asta was maneuvering it around some parking lots or making U-turns...
On about 50 000 km we noticed that the front shocks are also not working properly. So since we had to order a new rear spring, we opted for a full set of Hyperpro progressive springs from Touratech and changed all of them in San Diego, USA.
On 40 000 km BMW mechanics in Medellin, Colombia, suggested that it is time to change steering column and wheel bearings, so we did.
On about 45 000 km one of the heated grips stopped working. We solved the problem by fixing the broken contact on the wire. Soon it stopped working again. So we fixed it the same way again. So far it works.
I also had some issues with Givi Trekker Outback aluminum panniers and racks. The top box holder plate, which wasn't new when we left, started to crack while we rode very bumpy Patagonian roads. But apparently people at Givi already knew the problem and had upgraded the part into a more reinforced one, so as soon as I complained to them about that, they immediately sent us a new holder plate which now works just fine!
Also I managed to drop my bike so many times... And almost every time, it would be my Givi side panniers which would end up between the ground and the bike... So the panniers eventually became loose on the racks and Givi representatives in Bogota, Colombia gave me a set of new side panniers as a present for a successful adventure!
Linas' bike (2016 BMW F800GSA):
At 10 000 km one of the front fork seals started leaking oil. BMW dealership in Santiago, Chile repaired it under warranty.
At about the same time the something in the fuel tank cap broke an the cap wouldn't stay up when opened. BMW fixed it under warranty.
At 15 000 km in Peru, the fuel pump died just as it did on F650GS. BMW in Lima, Peru changed the pump under warranty.
Also, we used a set of chain each. Now we run on RK takasago chain. We used up two sets of tires. Now we are both rolling on Australian Motoz Tractionator GPS. We changed the rear break pads on F650GS (they weren't new when we left home) - we use EBC Brakes. We burned a few light bulbs each in the headlights and sprayed huge amounts of various chain lubes on our chains - we do it every 400-500 km and BMW cleans our chains for us once in a while...During the whole trip we only had only one flat tire - the front tube of Linas' bike got punctured because of the rubbing while the tires were deflated while riding on rough gravel. Took us 25 minutes to change the tube and continue the ride.
Every 10 000 km we do a regular bike service. The F800GSA is being serviced in official BMW dealerships to keep the warranty valid and for F650GS we sometimes do the service ourselves, or bring it to the dealership from time to time to get their professional opinion on what additional works should be done.
So this was the overview of how the bikes are doing. Knock on wood and fingers crossed so that everything continues to go so well for the rest of the trip!