The diagram on page 5.0 of our NSR250R English Service Manual shows the hose leading off the thermostat, and shows the spigot on the top [rear] cylinder head, but it's not clear that the hose should connect to it! However, it does!
The MC16 is the only model with this setup. Later models have the main [rear] cylinder head spigot in a different orientation. I think the small hose is to aid bleeding of the coolant system.
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Andy.
NSR-WORLD.COM
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