WR4 Thermo-Bob Kit

The WR and YZ450F are popular choices as snow bikes, and in those applications, the lack of a factory thermostatic control leads to coolant temps varying widely.  The carbureted bikes then have inconsistent jetting, and the EFI bikes end out overfueling, thinking the bike is constantly in ‘warm-up’ mode.  The Thermo-Bob 3 is a machined aluminum housing with a 180°F (82°C) thermostat inside, and modifies your cooling system to operate like automotive systems have for decades… keeping coolant flowing all the time through the engine, but not through the radiators until it is up to a selected temperature.

A full technical write-up when used on a Kawasaki KLR650 can be found here.