Found a post I made previously that might give some insight. MV Agusta F3 800....
I have serviced my rear hub and it does feel hot when I am riding hard/fast. On a 95F day riding between 70 - 120 mph for an hour it will be too hot to keep my hand on the hub and axle. Not instant burning but too hot to continuously hold. I don't really have rough hands so I would guess it is around 120-140 degrees F maximum? I don't use the rear brake generally during a ride unless I'm in a wheelie mood.
Thanks man. Just picked one up I'll see what temps i get. Just needing that sanity check. I have several bikes without a single sided swingarm so I don't have a good comparison point myself. Maybe it just runs hot. I'm almost certain the brake was sticking but seems like that bit is fixed now.