ORIGINAL: chuck993
I use cool power 15% or 20% pro pattern and fly all year, no storing of the plane for 6 months, etc. I run the fuel out of the plane then add after run oil.
Tower blamed it on rusted bearings, which seems to be everyone's excuse and refused to fix it under warranty. I store my planes in the garage, but I fly almost every weekend all year around.
The fact that you keep it running would lead me to beleive you keep the moisture from building up. I know allot of people keep thier planes in the garage, but possibly the availability of more moisture in the garage could be causing the issue. I had a 4 stroke engine (not the AX120) I kept in a porch with solid closed-in walls all the way around, but with a door leading outside, which i would go in and out of every day. I had rusted bearings. It did sit though for a month though un-run. One trick i do now is after a day or so i hit the engine with a hot hair dryer long enough to get the block so hot i cannot touch it. then i spin the prop over and over to get air into the hot engine. I think it steams out any moisture that builds up during the first day or so. I also now keep my plane in a 2nd floor living spoace. So far no return of rust.