| my 996r and 998r both in australia run 80-85C winter while riding,but in traffic do tend to run up to 110C; at this temperature I found I was splitting header tanks ( I stopped this occuring by replacing the rubber bung under the ignition key with a piece of turned delrin exactly the right length to stop the flat ( relatively ) top of the tank flexing and incourageing the tank to split along its top rear edge.If the bike doesnt run over 100C the water loss is negligible ; however if the bike has a split tank the riding temperature (80-85C ) stays stable long after the bike has increasing temperature problems while idling . This is because the bike requires less effective radiator area at large airflows;-- but the 996r-998r have marginal cooling efficiency while stationary (get hot) It appears the fan only switch on at 95C which gives to small a margin between the fan cooling and system pressurisation (boiling). I found this out by disconnecting the fans (2x) and measuring the engine temperature with an infra- red gun.I needed to do this because one of my 996r s consistantly overheated at the lights after 60kms of riding;-- the problem gets worse as the water level drops because it eventually starts to decrease the effective radiator area ( some of the tubes are not full of water) and the heat rejection starts decreaseing, next the bike then starts to overheat while being ridden ,this is more serious because the motor get hotter quicker than it will at the lights ( idling) I noticed that if I started to ride the bike that the engine temperature would drop back to 80-85C and I could get home without having to remove the tank and add water.A another common problem occurs when refitting the ballast tank line to the radiator neck,If you put the hose on too far the hose clip will stop the radiator cap from fully seating and this reduces the pressure that the cap will unload (dump ) at; this causes water loss from the cooling circuit into the recovery circuit , with the same results as above , because the cap doesnt seal well the ballast water isnt recovered to the cooling circuit on cool down ---overheating results
I recommend getting a 85c fan switch from motowheels, lapping the top of the fuller neck for a good cap seal,fitting a higher flow fan to the single fan models, getting the fuelling right,using water wetter (redline)
contary to whats stated above the thermostat job is to stop the engine running too cool under ' riding' conditions ; my thermostats appear to open according to my infrared investigations at 85C. The radiators easily provide enough heat rejection under riding condition with standard engines with less than 15% increase in power, but are marginal at the lights.
Ducati were recently selling off the DP radiators for the 998 cheaply!
Febur also sell decent oil coolers ( again available from motowheels) and these also add to the total heat rejection and will have the same effect as a larger radiator BREAKOUT  | 
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