How hot is too hot?

I have an 09 yz450f supermoto (street ridden). I have the trailtech vapor, the sensor is installed in the left side (hot side) radiator hose. What is the maximum safe indicated temperature? By the way I am running liquid performance race coolant (260 deg boiling pt).

255. You want to stay short of a boil, as when the coolant boils, gas bubbles form on the hottest part of the head, and at that point, the head is no longer being cooled.

I don't know if this will answer your question but I have an '06 with a Vapor on it. I ride in the desert (mostly wide open) but have never had the bike any higher than 190 in the tight stuff. When the trail opens back up it drops down to 145 - 165 (for the most part).


Ok, good. I shut er down at 240 the other day. If I were to get an even higher temperature coolant that doesnt boil over till X degrees, what would be the hottest that the bike could actually handle before it becomes dangerous?

I would not care to see coolant temperatures much beyond 290 in any case, regardless of the coolant used. The thing that concerns me is the engine oil and its ability to tolerate being that hot, and while the oil takes longer to reach any given temperature than the coolant does, but if the engine runs that hot for any length of time, the oil will get there, too.

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