Thermal Control System (Complete Kit) for KLR650 (all models)
 
The Thermal Control System by MCP corrects the KLR650’s factory cooling design by integrating a precision thermostat and full bypass circuit. This system prevents overcooling by blocking radiator flow until the engine reaches the optimal temperature (~195°F), allowing for faster warm-up and highly stable operating temps under all conditions.
 
By recirculating coolant internally during cold starts and regulating radiator access with a properly engineered thermostat, this kit significantly reduces thermal cycling, minimizes engine wear, improves combustion efficiency, and extends engine life. Ideal for riders demanding maximum reliability, especially in varying climates.
 
Kit Includes:
CNC-machined thermostat housing
Automotive-grade thermostat
High-temp rated hoses and fittings
Stainless steel clamps and mounting hardware
 
Technical Advantages:
Full bypass system for improved coolant flow during warm-up
Stable engine temps within a tight thermal range
Reduced piston/cylinder wear from cold operation
Improved fuel economy and throttle response
Direct bolt-on installation for all KLR650 models
 
Note: The aluminum blocks add 17.5mm of thickness to the coolant elbow. Although it generally works with larger tanks the largest option coming down low might not be compatible.
 
Engineered for serious performance — built for riders who want their KLR to run the way it should!
 
 
How does the stock KLR650 cooling system work?
From the factory, the KLR650's coolant is constantly pumped through the radiator as soon as the engine starts, even when the engine is still cold.
 
There is a stock thermostat in the KLR, but it only restricts flow to part of the radiator — the rest of the radiator is always open. This causes overcooling, slow warm-up times, and large temperature swings depending on riding conditions (cold days, downhill coasting, etc.). As a result, the engine often runs colder than it should, leading to increased wear, reduced efficiency, and inconsistent fuel tuning.
 
What does the Thermal Control System do?
It re-routes coolant flow to behave more like a modern cooling system. The kit includes a real thermostat (typically set around 195°F / 90°C) that completely blocks radiator flow until the engine reaches operating temperature. During warm-up, coolant bypasses the radiator and recirculates internally, allowing the engine to warm up much faster. Once the engine is warm, the thermostat gradually opens, allowing controlled flow to the radiator and maintaining a very stable coolant temperature.