TB3-V Thermo-Bob Kit

Description

Kawasaki cut corners in the Versys cooling system, and the Thermo-Bob modifies your cooling system to operate like automotive systems have for decades. In stock form, the Versys runs too cool when ridden in temps below about 80F. The cooler outside it is, the worse a stock bike is. Plus, the factory cooling system relies on surges of cold coolant every 30 seconds at the bottom of the cylinder to control engine temperature.  Look at the measured data on the right, look how slowly a stock bike warms up and how erratic the temps are.

The Thermo-Bob is a machined aluminum external thermostat with a coolant bypass. It allows coolant to bypass the radiator 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 cylinders to 190°F from 158°F… more importantly, it raises the operating temperature at the bottom of the cylinders to 180°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.

A full technical write-up on a KLR650 can be found here. The Versys data is shown in the plots above – it suffers from too large a factory bypass hole in the original thermostat.