Preparing to take off yesterday- what would have been the 3rd flight for the day.. warmed up the engine, about to clip in, and the engine suddenly stopped. All attempts to restart failed- presumed it was the recoil starter at fault. I had a spare one in the hangar, so I didn’t panic, and packed up.
Looking at the engine today I found that the starter was indeed faulty- seems like the spring has gone- changed it, but still wouldn’t start the machine- seemed as if there was no compression in the head.
Popped off the plug for a look, and noticed some shiny deposits on the plug- not a good sign. The mixture was right, so I knew that it couldn’t have just burnt a hole in the cylinder.
Removed the head to look at the piston and noticed a lot of debris inside the cylinder- and a piece of wire protruding right though the cylinder…. The wire has obviously entered the combustion chamber and penetrated the piston. There are some marks on the ports and inside the cylinder head where it has gouged out the walls, and some debris in the tuned pipe also. As yet uncertain where the wire came from… But seems to have come from the induction side of the engine- somewhere after the carb outlet…... Anyone seen this before?


Here are a few pictures-

Piston, with the wire protruding through the top surface at the bottom right.


Detailed view of the wire


Debris/soot in the cylinder- due a de-coking anyway after 120 hours. Visible damage to the edges and the piece of wire visible at the 5o’clock position


Damage to the cylinder wall and ports


Detailed view of the ports


Detailed view of the ports


Detailed view of the wire, and damage to the ports


Damage to the cylinder head- contact with the wire.


Thankfully it happened on the ground, and not in the air.


Regards,

GD