I am doing a 50 hour inspection, valve adjust, etc. on my Jabiru engine. I bought a borescope last winter and this is the second time I have used it to look at my cylinders and valves. Yesterday I was concerned to see strange discoloration in one combustion chamber that I didn't see in the last inspection.
The white deposits run across the combustion chamber, over and under the exhaust valve head and seat.
It was a puzzle but the engine runs good and has good power. Now I think maybe the discoloration is leftover lead deposits form previous owners running 100LL. The previous owner had problems with lead fouled plugs and started running Decalin. I have always run auto gas. That cylinder used to run extremely rich and cold and was previously carboned up. Since my manifold mod that cylinder is running much leaner and hotter and the carbon deposits are burning off which has exposed the lead I think. It looks like the lead is burning off the seat first. Do these deposits look familiar to anyone?
The white deposits run across the combustion chamber, over and under the exhaust valve head and seat.
It was a puzzle but the engine runs good and has good power. Now I think maybe the discoloration is leftover lead deposits form previous owners running 100LL. The previous owner had problems with lead fouled plugs and started running Decalin. I have always run auto gas. That cylinder used to run extremely rich and cold and was previously carboned up. Since my manifold mod that cylinder is running much leaner and hotter and the carbon deposits are burning off which has exposed the lead I think. It looks like the lead is burning off the seat first. Do these deposits look familiar to anyone?
