I agree with your thinking and looked closely at the carb, fuel pump, filter and fuel lines. There is enough "lawn dust" for me to see that the fuel system seems intact and functioning properly. At the time of the fire the engine was running smoothly. I did smell what obviously turned out to be burnt oil and was pondering that smell for a short time when the "Hot cylinder Head" alarm went off. I shut it down and climbed out to find a smoky fire on the cylinder head just under the valve cover and alongside the spark plug. What appears to be the sensor for the cylinder head temp probably requires replacement along with some of the attached wire, hence my initial question concerning the shroud.
About 5 years ago I had another fire caused by dried grass which was ignited by the muffler and I understand your comments on grass fires. The fire was located under the hopper close to the blower discharge. The three lessons I learned from that encounter were 1. When your wife runs out to tell you your on fire, believe her. The warning lights will verify that she is right. 2. The area under the hopper should be blown out more frequently and more thoroughly then before. 3. Electrical repair is much easier when you have a manual and the proper solder iron. 4. Wire color-coding abilities are more important then knowing how to count to three :laughing:
I noticed that one of the bolts holding down the valve cover was much darker then the other three-this would be the bolt nearest to the head gasket temp sensor. The temperature on that bolt had to be pretty high at some point in time, which makes me wonder if I have a leaky head gasket or bad head. That bolt tells me that there might have been a "good" heat source in that area. The residue left behind all points to an oil fire and the only place where gas could have contributed would be around the fuel pump hose fittings but they were in very good shape and did not appear suspect.
I need to take a break from this for a day or two while I attend to other needs but I appreciate your observations. I'll be back soon.
As an aside ( which I am rather prone to do ) my workshop is an old farm house on a friends 1000 acres.
They are grazing on land that was previously horticulture so there are drainage ditches everywhere.
They originally rotary hoed some of the slightly flatter but soon realised it was a waste of fuel as the ditches held rainwater really well .
The farm is in a rain shadow and the black fella name means "don't rain'.
Thus a real tractor mounted slasher is of limited use so they mow with a fleet of Cubs when the cattle can not keep up.
After 2 deck fires, all of the mowers now have fire extinguishers fitted.
However when talking about this to a local mower shop they laughed when I suggested fitting extinguisers as an option.
Apparently drink holders, sunnies holders, phone holders & charging ports are far more important accessories.
I do 2 to 3 fire repairs annually, all of them are deck fires from accumulated clippings.
We usually get a few weeks of 100F + days and hat tends to dry out the glass, just a little.
