Some folks have posted, either on this forum, or another, that the head of their CB750 (CB900?) clocked in at, or above, 300 F, using an IR Thermometer! This was when their bike was at operating temperature. Meanwhile, the oil, in the pan, was at 250 F. I agree, use a gasket -- they are still made, so why risk it? Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII