One of the best bikes I ever owned was a BMW R1100S, the boxer engine sport tourer with a hint of Ducati with twin under-seat exhaust and single sided swing arm. Gorgeous bike, to look at and ride.
Sadly, when the input spline shredded its teeth and cost me £1,500 to fix (back in 2007) it had to go. I was told by the mechanic that all boxers shred their teeth eventually, fine when moving, it’s sitting at idle when the opposite cylinders knock and fracture the spline shaft. He reckoned all boxer engines suffer from this at some point, the main reason I would never own one again… sad really as great bikes and I love the tele-lever front suspension.
Hopefully the later models like the 1250 are much better. If they make the shaft properly and copper grease it then happy days. They are so popular they must be better by now! Enjoy