The luck of the draw...
After 4 bulletproof and oil-tight 530's, I was beginning to think that rumors of oil consumption were overrated... but my current bike had started to consume oil around 30 hours (now at 66). My first response was to doubt my data collection methodology, but eventually it became hard to deny that I had to add oil after a day of riding. The rate of consumption didn't seem to change... it just seemed to drink oil. I searched for reasons why this could be happening, decided that it was probably not because I had been a bad person or that KTM hates me and instead that something mechanical was amiss. So, I decided to tear in.
The short version of the story is that I found an intake valve guide seal lifted off.
While I was in there, we replaced all 4 valve guide seals, and found that the other intake seal was barely in place (the seal lifted off by hand) while the exhaust seals were super tight, and due to oil buildup on the exhaust valves, the exhaust valves were binding in their motion (fixed with a good cleaning). I replaced rings as well, which were slightly worn, I can't find a spec but they were both around .025", where new should be about .015"... I doubt this was an operational issue.
No real time on the bike since the repair, but I'm sure we've got the oil consumption fixed. At the end of the day, for a reasonably skilled mechanic, this job should take about 4-5 hours if you are not drinking beer. An intake valve guide seal (59036027000) is $4.74, a head gasket (78030036000) $30.22, and a base gasket (78030035000) $5.08, so if your bike is drinking oil, you're probably less than $50 from fixing the problem, a few dollars more if you opt to replace rings as well.
I took pictures and handwritten notes to do a writeup on the procedure, but don't have time to post that right now. Suffice to say, it's not that bad and doesn't require any rocket surgery.
A few pics from the operation:
Cylinder head before:
After we took the valves out, a buddy dropped the whole shebang in a parts washer for a few hours, this was the result.
Something is missing! I'm sure of it! I just can't figure out what...
It really does come out, but it takes just the right angle:
It'll be back to its old shenanigans in no time.