Used to own an '06 625 SMC, the supermoto version of the SXC. Super fun bike, but lots of problems. Off the top of my head, waterpumps grenade, rocker arm bearings need to be changed every 10-15k miles before they explode and take the camshaft with them, and oil seals on top of oil seals. Bought my bike at 20k km's and sold it a couple years later at 28k km's. In that time I did the output shaft seal, shifter seal, oil filler cap seal, resealed the valve cover. Sold it needing a cylinder base gasket, and I think starter seal. Those were the major ones, really the engine needed a full tear down to replace every single seal.
My favourite issue on that bike is KTM drilled one of the exhaust header screw holes straight through into the open head, guess where oil was leaking from... Wasn't just my bike, I think it was all of them.
Outside of the issues, I really loved riding that thing. Rattled like a paint shaker, in a kind of charming way, as long as I wasn't on the highway. Fueling was probably the best I have ridden on any bike, don't know what was done to my carb, but it was a thing of beauty.
Not my picture, but the red wire shows the path from the exhaust header screw hole into the head