flew some 30 minutes. Fairly icy conditions, so pull the CVV (carb heat). Suddenly the engine shook as h..%$%$..ll and I lost RPM. Quickly looked where the wind was coming from, and were to land if necessary, while closing the CVV. Sound and shake stopped. Without further delay flew some 10 minutes to the next airport. In landing pulled the CVV again, and there it was again: sudden shake (very, very much), and loss of power. Could land safely, though. Had an angel on my shoulder..
afterwards checked the engine and it sounds like heavy disbalance: as if one cylinder is totally flat.
Today I dismanteled the engine together with some friends, and I'd like to share my experiences:
After taking the cylinder head off, it became clear the outlet valve wasn't working, and was stuck in 1 mm open position. Loss of compression cleared. But why - and why in such a sudden. And what was the relationship with the CVV?
after carefull search we found the following:
A ½" piece of 1 cm tube from the carb-heat system was the problem. These tubes are used to center the exhaust pipe in the carb-heat tube. There should be 6 of those little b...s in the pipe.
And I only got 4 left. One got loose during flight, and was sucked up in the carb-heat box. After that it was sucked into the airhose to the carburetor, through the carb, into the cylinder (yes, through the inlet valve), took some time there (the 10 minutes the engine looked OK again), and tried to leave through the outlet-valve. There it got stuck, and I lost power and experienced a heavy disbalanced engine.
We removed the piece, and looked at each others shoulder for the angel that should've been sitting there. Not only could we land safely, but the 1,5x1,5 cm piece of aluminum visually did not damage piston, valves, rubber carbframes or anything else. Not even my confidence, for I really like this engine and hope it will stay with me and Foxy a long time.
This week will bring thorrowly looking at the cylinderhead and valves, then build her up again, testrun and fly back to her own hangar.
In my annual a throw check for all rivets has been written down. And some comfortable chairs to put onto my shoulder. For my angel.
angel
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