Greg,
The 140L had it's share of problems, I'm not sure if it affected all of them or just a few.

The problem began right at the start, the engine would start just fine, be running nice and rich for about 2-3 minutes and then all of a sudden the smoke trail would cut out from the exhaust for no apparent reason, then it would overheat and quit. This happened on the test stand on the first run and on the next three runs. Even with a perfectly balanced prop the engine was shaking violently.
After about 5 runs and alot of tuning on the needle and regulator, I thought I had it running half way decent and installed it in the plane, took it out and test flew it, of course after 3 minutes the smoke stopped and the engine quit. After replacing a bunch of parts including the regulator diaphram and having several YS experts look at it and try there hand at tuning it, we came to the conclusion to send it back.
I had a buddy who offered me a Patrick 40 size Ultimate with a O.S. pumped 91 4 stroke on it for the 140L, of course I jumped all over this offer, he sent it in, but I'm not sure of the outcome.
I heard about some issues they had with it in regards to the piston and or piston ring, but it's been awhile so I not positive about this, I would do a search on the engine and see what you can find.
The few flights I did have where it ran fine for the entire flight, the engine was a real powerhouse, perfect for the plane.