Don't forget that bare aluminum, or even painted aluminum, sometimes reads incorrectly with non-contact temperature guns because of how fast aluminum radiates heat. If you want to get an accurate reading you have to stick a temperature probe right on the aluminum.
Honestly I don't know a thing about what temperature these engines typically run. In a relative sense my 1980 K feels hotter to ride than both of my BMW's which have their cylinder heads sticking out the sides, and it feels cooler than the other inline-four, a 2002 Kawasaki Concours 1000, which I owned for a short while. That bike had full fairings so the heat would collect and shove its way right up into my face, plus it was a big motor with a big radiator tucked under the same fairings just in front of the exhaust.
If you suspect that one cylinder is running poorly compared to the others, go for a ride to get up to full temp, turn off the bike, and immediately aim your temperature gun at your exhaust headers right where they start to curve. Compare the numbers for all 4. If they're not all fairly close to each other, within maybe 20 degrees F, the outlier(s) are suspect.
The lean factory jetting of our bikes means they probably do run a little hotter than they should, even though they run great in factory trim. If you have vacuum leaks that'll make the heat worse because a leaner mixture makes more heat.
