Could be thermostat stuck open, makes sense the way it's acting. It IS thirty years old. One of the things still on the to do list.
This thing will cool all the way back down to below the first mark on the temp gauge after warming up to mid range, being cold does appear to effect combustion efficiency. It doesn't sputter or miss, but there is a noticeable (to me anyway) difference between dead cold and warmed up.
Yes, flushed and reflushed with distilled water. I couldn't really tell what color the original coolant was supposed to be, it was pretty much a darkish black/brown mess. Probably tap water with a little bit of coolant residue.
It was refilled with the proscribed 50/50 mix of silicate free/aluminium safe antifreeze. I was just glad that it didn't leak like a sieve after flushing it.
But since I have to return to work, the new thermostat will have to wait just like the other things that need to be replaced due to age.
Thanks for the insight though, it's appreciated.
(Still, nothing like learning something new to make you realize how much you don't know. l never really considered radiators and such on motorcycles before getting the VN.)
New front tire & rear tire
Brass fuel inlets
Swing arm cleaned and lubed
Final Drive oil
Cooling system flushed and filled
Mosfet R/R and relocated
Trying to achieve Anodized Red Chrome paint... from a rattle can...