Thermo-Bob results
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This kit is for 1984-2005 KLR250 bikes... please see other products for the version that fits newer KLR650s, or other Kawasaki motorcycles.

Kawasaki cut corners in the KLR cooling system, and the Thermo-Bob 2 modifies your cooling system to operate like automotive systems have for decades.  Thanks to the dual radiators, a stock KLR250 runs too cool when ridden in temps below about 100F. 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.

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 160°F… more importantly, it raises the operating temperature at the bottom of the cylinder to 185°F from downright cold, (ie as cold as 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 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 650 can be found here.  The 250's dual radiators make a stock bike's temp swings even more erratic than a 650 - see the before and after plots above.

  • Item #: TB2-R

Thermo-Bob 2 for KLR250: ALL MODEL YEARS

Price: $129.00
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