This kit fits all years of the KLR600 and KLR650. It also fits the European-based KLR650B (Tengai) and KLR650C. It fits bikes with stock as well as aftermarket 6.6 gallon fuel tanks, but will NOT fit under the aftermarket 10 gallon tanks. For those applications, we have put together a “Thermo-Bob 3” kit. You can find it here for 1987-2007 bikes, and you can find it here for 2008-2018 bikes. There are no aftermarket oversized fuel tanks for the Gen 3 bikes… yet.
Kawasaki cut corners in the KLR cooling system, and the Thermo-Bob modifies your cooling system to operate like automotive systems have for decades. In stock form, the KLR runs too cool when ridden in temps below about 80 – 85F. 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… just look at the plots of actual measured temps.
The Thermo-Bob is a machined, hard-anodized 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 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). It should eliminate the out-of-round cylinders that are common to the KLR as it ages which usually results in increased oil consumption. The warmer temps should extend engine life as well as increase oil change intervals, and improve economy by a few MPG.
I’ve got 191,000 miles on my KLR with a Thermo-Bob and have never rebuilt the engine… and still only burns about 15 oz. of oil every 1,000 miles. 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 can be found here.