New guy with question on radiator overflow on WR450F

HI all, new to the forum, new to dirt bikes and new to my WR450F!


I went out over the weekend and did some trail riding with some new friends, temps in the high 80's and it was more of the slower, tight woods riding than the fast, open riding.  At some point into the ride, about 45 minutes or so, we noticed my radiator starting to overflow.  We stopped, let it cool down, and then rode again and the overflow repeated itself.  At the end of the ride I barely had anything left in the radiator.


One of the guys I was riding with had suggested using Evans coolant, along with possibly a new water pump and a high pressure radiator cap.  Doing some research it appears that Evans is a good place to start.  I pulled off the water pump cover as well to look at the impeller, which shows no damage.  Is the impeller supposed to spin while the bike is shut off or just move slightly in both directions?  Just wanting to check to see what's normal....


So my question, should I just start with the coolant, or do the Boyeson water pump kit and the radiator cap as well, or some combo of the 3?


Just want to make sure I'm doing the right thing, thanks again for the help!

Clean the radiator of all internal corrosion

Add waterless coolant

Add a 1.3 bar cap

Correctly jet and uncork the motor so it runs at the correct temp


If you find yourself needing 12tooth front gearing, THEN you might need fan or oversize radiators for that kind of riding

A boyeesen is a waste of time, as the radiators will not move more water than they do now.


You need to fill that siphon hose to the catch tank with coolant, so it will siphon it's way back to the radiator as it cools off.....


When the motor is running, open the radiator cap and watch the's very slow, and barely noticable.....which is normal.

Ok, cool, thanks! Assuming I would open the radiator cap when I first start it up before out gets to hot?

Ok, cool, thanks! Assuming I would open the radiator cap when I first start it up before out gets to hot?


Do not open a hot radiator. You could be burnt.

Thanks, I assumed as much, just never heard of opening a radiator at all with a vehicle running.   :thumbsup:

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