Originally Posted by EXflyer
Wonder why it was only one piston as there usually is damage to the others also but to a lesser degree as the hottest cylinder would have the most damage.
I don't know either.... There has been very little info provided so any explanation would just be a total guess on anyone's part.
There are details specific to the design of the 912 that could account for just one cyl having a problem....
With the two carb's each connected to just the left or right side cyl, a 912 is essentially two engines connected via a common crankshaft.
It is easy to accept that there could be a problem on one side that didn't exist on the other.
There is also differences between the front and rear cyl. on both sides. With the designed shape of the intake manifold, the induction flow for the rear cyl has to make a sharp turn immediately after exiting the carburetor. This results in a well known condition of the rear cyl. always running slightly leaner than the front cyl. (this can often be seen when inspecting the condition of spark plugs).
So it would be understandable that if a specific condition became marginal, that one of the cyl may have been negatively affected when the other wasn't (though Jim never mentioned which cyl had a problem).