Thank you for good information.
Since I used to work in a hot strip mill in close-to-semi-tropical location (in summer 120+ F 100%RH in the mill), I cut, haul, split, and stack firewood even on 100+ F summer days.
I experienced a lot of vapor lock problems, not knowing what they were.
I was furustrated, but I thought it was just a "bad behavior" of my saw.
Now I know what it is. Thank you for the countermeasure suggestions, too.
Next summer, I will make sure I take all 4 saws with me.
Noko