I used the 46 LA in all my fun fly planes. One thing I ended up doing before I ever fired them up was to remove the head screws one at a time and put some thread locker on them. I think every engine I had except one had the head screws loosen up on them. I used 15% nitro with the OS #8 plug in all of them. Other the then tune up run I gave up any breaking in at all, once they ran and would idle I took off and flew the plane. After about the third flight no more gray crap out the muffler. Never once have I ever had a problem with an LA. As much as I didn't like the 40 they still ran well, just way under powered compared to the 46.
Gene