Riding to work this morning ambient temp around 8c. Running temp around 80c, stopped at lights for about 3 minutes temp went up to 104c. Rode away and temp stayed at 104c for the next 3 minutes until I got to work. When I turned off the engine the fan was running madly. Left it sit for 30 seconds while I unlocked the gate. Started again and the temp quickly dropped to 90c. Does the rapid rise to over 100c indicate a thermostat issue? Thanks.