Thermostat YZ4B
The Thermo-Bob 2 is a machined, hard-anodized aluminum housing that bolts directly to your cylinder head. It allows coolant to bypass the radiators during warm-up, speeding warm-up and eliminating the surges of cold coolant year-round. It also raises the operating temperature at the top of the cylinder to 195°F from 158°F… more importantly, it raises the operating temperature at the bottom of the cylinder to 185°F from downright cold, (I’ve measured temps below 30°F). The warmer temps should extend engine life as well as increase oil change intervals, and improve economy by a few MPG. It was the first product to ever receive a 10-out-of-10 rating at Patman Racing, and was strongly recommended by the late Cary Aspy, who was the original developer of the 685 and 705 KLR big-bore kits. Cary also liked how this gave more consistent carburetor jetting.
