Temperature Gauge Problems?

She's up an running like a top!!!



I'm so very happy to be riding again, although I'm taking it easy since it's been so many years since I was last on a bike.



I had a young man change out the mechanical seal (thanks again, Doward!) for me and get her going. Everything seemes to be fine with one exception...



The temp gauge would climb up to the maximum for a few minutes and then come back down to normal, but now it just goes to max after a few minutes of riding (or idling) and stays there. The bike runs fine and I can put my hands on the cylinders and crank case for several seconds so it's not like it's heating up to a meltdown of biblical proportions.



My mechaninc took the thermostat out of the parts bike and tested it before he installed it, and ended up getting an O-ring kit for putting it all back together. I put 42 miles on it without any signs of trouble



Any suggestions?