The original 115's had an induction issue that was frequently noted by some in knife edge and inverted flight. Some had it, others didn't. There have been several people working at home to develop a consistent fix, with some being more effective than others. The new BME owners took a look at some of them and appear to have gone with a design that takes care of the early engine issue.

Those that already had a 115 from the original manufacturer are being provided the fix for a cost of $6.00 to cover the shipping. The new engines incorporate the fix. I don't know specifically what the fix is. I'm still waiting for a reply from BME about a question on the subject.