Hi mate, i have a gen 2 RSVR rather than a gen 1, but your temps sound pretty similar to mine, when riding normally the temp is usually around 78 -81C, but when stopped at traffic lights usually rises up to 87 - 90C, if it's a hot day maybe even up to 94C
The passage below is taken from the RSVR handbook, hope it puts your mind at ease a little.
The coolant temperature display reads " - - -" when the sensor detects a temperature below 34°C (93°F). When the sensor detects a temperature between 35°C (95°F) and 114°C (237°F), the display provides actual temperature indication. Temperatures between 115° C (239° F) and 135°C (275°F) are displayed with a flashing indication. In addition, the warning light will come on to indicate a dangerous condition. The display will flash for temperatures above 135°C (275°F) (again, the warning light comes on).