I've never seen a fan needed on an NSR, and I've ridden and worked on them in exceptionally high heat and humidity, in several countires. That goes for MC18s too, not just 21/28s.

Optimal temperature for a 2-stroke is around 62~65 degrees. I've seen NSRs sat stationary in traffic reach around 100 degrees, but will drop to 80 degrees almost instantly the moment they start moving and there is airflow across the radiator. Normal NSR250 operating temperature should be around 70~75 degrees.

Running without a thermostat wouldn't be my recommendation unless racing. As Dave says, correct warm-up is something most people don't even do when a thermostat's fitted!
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Andy.
NSR-WORLD.COM

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