hi guys, just a few comments if I may. To understand why leaner than stoich fuel ratios do not ccause hotter gas temps try thinking of it this way: At stoich ratio (14.7 A:F)all the fuel combusts and makes heat, any air in excess of stoich must be heated by the combustionof the stoich amount, thereby lowering the temp. in the real world it may not be possible to get full mixing of A and F so slight increase in A my yield slightly higher temp.
As for boundry layers, the area aroiund the exhaust port has no such protection, and for this reason sutained ops with poor lube, lugging, dirty filter bypassing, etc may cause damage to piston or cyl before detonation occurs. Good maint and consistent use paying attention to vibration, sound, and smell of saw is the key tot longevity.
in a related topic the use of a SHARP chain with proper gage depth does a lot to protect the saw's engine too. Just my 2 cents, Dave.