TB2 External Thermostat Kit

The Thermo-Bob TB2 is a cooling system modification kit for Kawasaki KLR600 and KLR650 motorcycles. This kit aims to improve engine operation by modifying the cooling system to function more like automotive systems, which have used thermostatic controls for decades. In its stock form, the KLR often runs too cool, especially in temperatures below 80-85°F, leading to inconsistent engine temperature. The factory system also relies on surges of cold coolant to regulate temperature. Constructed from machined, hard-anodized aluminum, the Thermo-Bob TB2 features an external thermostat and a coolant bypass. By allowing coolant to bypass the radiator during the warm-up phase, it significantly speeds up the time it takes for the engine to reach its optimal operating temperature. This also eliminates the jarring surges of cold coolant that occur in the stock system. The Thermo-Bob TB2 kit raises the operating temperature at the top of the cylinder to 195°F (from a stock 158°F) and, more importantly, raises the operating temperature at the bottom of the cylinder to 185°F (from much colder, potentially below 30°F). These warmer, more consistent temperatures are intended to help prevent the out-of-round cylinders that can occur as KLR engines age, which often leads to increased oil consumption. Additionally, the warmer operating temperatures may extend engine life, allow for longer oil change intervals, and potentially improve fuel economy by a few MPG. This kit fits all years of the KLR600 and KLR650, including the European-based KLR650B (Tengai) and KLR650C models. It is compatible with both stock and aftermarket 6.6-gallon fuel tanks. However, it will NOT fit under aftermarket 10-gallon fuel tanks; for those applications, the Thermo-Bob 3 kit is recommended.