Spears Racing High Pressure 1.6 Radiator caps:The simplest and the most inexpensive way to avoid boiling your engine, especially important on over-stressed Lightweight Race bikes cooling systems, is to Pitch the stock 1.1 kg/cm2 radiator cap for a 1.6 Radiator caps. While raising your cooling system’s maximum operating pressure does raise your cooling system’s boiling point and therefore helps to avoid boil-over, it does not lower the engine’s operating temperature prior to boil-over. It simply allows your engine to continue to operate at temperatures higher than it is engineered for.
Water boils at 212 degrees, and for each pound you raise the system pressure, it raises the boiling point 3 degrees. A 1.1 kg/cm2 cap converts to 15.9 psi. Most factory race bikes use 1.8 kg/cm2 caps (which are 26 psi). fit on any Japanese radiator; CV4 sells 2 kg/cm2 caps for both European and Japanese bikes.