Just for the heck of it I bought an infrared digital thermometer and did some testing on my motor. At 26deg C or 79 deg F air temp doin a speed of 25 mph or 41 km on a 28:1 mixture and a 40T sprocket the head by the sparkplug was running 270-280 deg F. At idle it was about 230-240 F and flat out around 290 deg F. Saw 310 once after backing off flat out but it immediately started dropping from there. As a side note when I replaced my head studs I made them longer so as to be able to double nut them and install one at a time without having to pull the head off. Basically an extra 1/4-3/8 inch longer so they sit about the top of the cylinder fins. Probably doesn't do a heck of a lot but does aid a little bit more to disperse heat from the head with the air passing over it. Fwiw.