I dunno if i am lucky or what. i used the automotive carburetor parts cleaner that comes in a gallon can and soaked all parts of an engine i had that ran crappy. it was pretty well gummed up and really hard to turn over. I took it apart as much as was possible, then soaked everything except the carb and any O-rings and soft parts in the stuff. I dunno if this should have damaged anything or not. when i was done, i blew, rinsed everything out real good and then soaked the whole thing in automatic transmission fluid. then put it together and ran a couple tanks through it before i flew it again. I ended up with a motor that runs perfect. it used to cause at least 5 deadstick landings per day of flying before the harsh cleaning. now it runs like a top! so like i said, i don't know if this is good advice or not, but i would not hesitate to do it again.