First of all, the official Kawasaki “RACE-KIT” manual specifically states to remove the thermostat for {increased cooling efficiency}.

However I am also of the opinion that there are numerous, and I mean many, errors in that manual.

That manual is not made up by the Factory in Japan, but what looks like to me, their Kawasaki UK Raceshop, soooo,

I run a Digital temp gauge and find that my engine runs about 70 degrees centigrade without the thermostat, which is pretty cool. About 82-85 degrees centigrade with the thermostat. SO WHICH is Cooler? I haven’t run a thermostat in years!

However, what has been stated about the coolant flow not being restricted by a missing thermostat, allowing the coolant a “to short of dwell time in the radiator”, would seem to make sense, but this has not been shown to be the case in my tests.

Ken H2Os

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Check this out,

I rigged up a 91 ZX7 radiator to my flow bench and flow tested it. I then flow tested a radiator housing with a modified, fully opened thermostat.

Obviously when one looks at the size of the opening of the fully opened thermostat, it is much larger than all the “VERY TINY” passages through the Radiator. The radiator was definitely the restriction in this hookup. When flowing through the radiator housing with or without a thermostat, made no difference to overall flow through the radiator,. So after flow testing just the rad. and then flow testing the rad. with both a therm and without a therm, made no difference.

The radiator IS the restriction. I would like to believe Josh’s theory, but Its not playing out on the flow bench, or in actual temp testing


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