I know things... A lot of things.
Join Date: Feb 2015
Motorcycle: GSXR 750 K4
Re: 2011 Gsxr600 leaking coolant from overflow
As said, check you manual regarding the proper coolant level in the reservoir tank. If you filled it too high, it might overflow under otherwise normal conditions. If you hear it boiling, or if the coolant gushes out shortly after you stop the engine. then the cooling system can't develop pressure. Check the procedure for purging the air out of the coolant in the service manual and then, as suggested remove the cap and inspect both it and the sealing surfaces of the radiator neck. Try to take a photo for us to see.
If you see debris, between the rubber of the cap and the surface of the neck, it's probably depositions from the boiling coolant that escaped through the gaskets, so the cap should be replaced with an OEM part, especially if it was not OEM. If you see signs of corrosion on the neck (likely pitting), it would be a sign that your coolant is not properly formulated and allows corrosion to take place. This will be more pronounced at the interfaces of dissimilar metals, as in the neck-cap interface. In general and especially if your problem turns out to be due to sealing problems and not just due to overfilling or insufficient purging after a coolant change, I'd suggest reconsidering your coolant, especially if you don't know what's in there. Go OEM unless you know that some other mix is suitable, as specified in the service manual.