I had a Saito 150 mounted inverted that was on an airplane I bought at a swap meet. I had flown it 3 or 4 times. It was easy to hydro-lock. It had been flown quite a bit before purchase by me. It was my first Saito. I quickly learned to be sure it or any other engine inverted is clear of fuel in the cylinder before applying an electric starter! It tried to run then a loud bang occurred. Upon removal I saw a crack in the bottom of the crankcase. Upon tear down I found the crankshaft sheared next to the counterbalance. It had been cracked part way around the shaft for sometime because you could see the brighter metal in the smaller break of the crank that was left waiting for me to finish it off. I since have made it a habit of opening the throttle before applying glow plug heat and cranking by hand backwards several times especially after filling with fuel. This eliminates any fuel that may have found its way into the cylinder during fueling process. I have watched others with similar problems especially after filling with fuel before first flight. The engine comes up against compression and stops because of excess fuel in cyl. head. Myself and fellow flyers have had no problem with hydro-lock when using this method.