Have a look up behind the rad where the thermostat is. I *think* it was the hose clamp into the thermostat, but may have been the front bolt on the thermostat itself. It did require some disassembly, but I did not drain coolant or pull the rad. Get a small 1/4" ratchet with a 8mm bit or a ratcheting 8mm spanner and you should be able to tighten them. While in there, give every hose clamp (6mm) a couple turns to sung them up. Heat cycles make rubber softer and when they build these bikes they don't have time to heat cycle and re-tighten everything.