Yep...sounds lean to me. I had a 46 LA and it would do the same thing. That little engine ran just fine though at a richer setting. Richen it up a bit and see if that doesn't help. Also
when you fly your plane, do you run the tank all the way out? If you run the tank half dry, then refill over and over, the fuel gets a lot of crud from exaust residue. It's good to empty the tank as much as possible before re-fueling.
this sounds like good advice. I never really thought about it, but it makes sense.