I too have had the pleasure of working with Youxin at his home on several occasions.
While a CLA is nice, it is the tricky repair jobs that also stand out. Here are a couple examples from yesterday - my M's are back to perfect function now!
1) slipping shutter winder.
Youxin CLA'd my first M4 a couple years back, but we couldn't figure out a problem with the winding assembly. Every few winds it would advance the film just a tad further than normal with the winder lever traveling just a bit too much. Looked at it a year ago while doing a CLA on different M - not quite there yet. Some time ago Youxin spoke with me and said he had it figured out..
Ahh, the culprit, a part buried deep in the winding assembly:
[M9, 75/1.4 lux - in-camera jpeg]
..and success!! - smooth and perfect winding every time. I must say, reassembly was quite tricky, involving a fairly complex sequence of cocking shutter, partial assembly, firing shutter, tightening, winding, rotating - the winder is like a little puzzle.
2) My second M4 was out of commission, having bumped a prism loose - aahhh!
Luckily it was the middle prism, the easiest to fix:
While the UV optical glue cured, Youxin shared a bit more about the fine points of viewfinder alignment, and how even out of the factory there is some variation if you know what to look for.
btw - it would seem word of his planned departure for the China Leica Exhibition is out, and quite a few units are being sent for CLA, so don't delay..
I think he is still accepting image submissions for the Exhibition for the next week or two, so if anyone wants to send along entries, I'd contact him soon. Not sure of the selection process, but it covers the early days to today.