Last sunday, i took out the engine to install rev max. So took the chance to change the bearings since i was at it i thought might as well do some cleaning up. The piston had some carbon residue on top and a ring of slight brownish patch around just below the ring. The cylinder sleeve has some black patches at the exhaust ports.
So i used scotch brite n clean away the residues on both the piston n cylinder. took out the con rod n clean the inside of the piston as well.
Changed both the bearings and assemble back, everything looks ok. turn the crank shaft by hand it was normal and there were no signs of binding.
After which went to fly, first flight - richen the engine abit as bearings are new. Flight was mostly hovering and slow figure 8 using only normal curves to let it run in abit. Felt it was smoother then before i change the bearings. back plate temp was cool . I thought all was good.
2nd flight - started with normal curve , flew around landed n tested back plate, temp ok. then switch to idle 1. headspeed higher. responsive and quite good power, so i thought great the bearing change works. Then i test the rev max on idle 2. i set the limit too low so proceed to land n increase the limit.
I throttle up again on my normal curve, while hovering at eye level,can hear the engine start to get higher pitch like leaning out. then followed by metal sounds then engine cut...
i thought it was the fan came loose. When i came back, realized the con rod broke n was shocked to see the engine case broken with 2 extra holes!!
Dam what went wrong?
-con rod broke, piston sides broke, engine case broken with 2 holes
-cylinder looks ok.the rest of the engine looks ok except for scratches inside the casing.