Oil Cooler Questions?

First?- Does anybody know of a company that makes an aftermarket oil cooler for late model YZ450f's (2007 specifically)?

Second- Does anybody know what exactly the flexible oil line does that runs from the top of the case (the line that comes out right next to the oil dipstick) then runs to the right side of the bike and reattaches to below the oil filter cover? I ask this question because I heard that this line is some sort of overflow line and if I built an oil cooler to insert in this line, that since it is an overflow line that there wouldn't be enough pressure to circulate any oil through this line, hench no benefit of an oil cooler placed there.

Let me know what ya, know! Thanks for your time!

I want to run an oil cooler on my 07 as well, 'cause I'm converting mine to street legal supermoto, and want as much oil volume and cooling as possible.

I looked at that oil line too - sure would be simple to tap into it as you state, but I fear that it is a non pressurized line as you say and oil wouldn't circulate.

Her is the only solution I have found - it's not available, yet, but hopefully soon. I intend to buy one - hopefully street price will be around 800 or so.


The external oil hose on the '06/'07 YZ450 is a vent line only. Its purpose is to balance the internal atmospheric pressure of the oil tank with that of the crankcase to assure oil flow to and from the tank. It can't, therefore be used as an oil cooler line.

Spoke to PWR today - rep said they are seeing a reduction of 41* in oil temp and 31* in coolant temp with their setup. Oil volume is increased by 100cc.

Since the coolant cools the hot oil, and no extra area has been added to the radiator core, I find it impossible to believe that they are getting any reduction in coolant temperatures by adding more heat to the coolant. This is made all the more difficult to believe by my experience with automotive radiators with coolers in the bottom, or return, tank of the radiator. Water in that tank has been through the radiator, and has been cooled as much as it will be on that go 'round. Any heat the water takes from the engine oil via a cooler placed there is carried directly into the engine and added to whatever heat the engine already produces. Evidence that it worked would actually come in the form of increased coolant temperatures exiting the engine.

Mind, I'm not saying it doesn't work. I'm only saying that you should learn to identify certain things as stuff you shouldn't step in.

The only thing that I have found in searching the forums is some guys saying that a certain oil additive is working well to reduce temperatures. (I don't remeber, but something with a "C22" in it I think!) Grayracer, do you think a stand alone radiator type oil reservoir/cooler would help take some of the heat away from the oil if you could get it piped in a pressure line somewhere? I know some of the Factory KTM bikes that race off-road have a setup like this. Does it work, I don't know! Maybe they were experimenting.

An air cooled cooler works, too, but the water cooled cooler is more effective, and so can be made smaller to accomplish the same thing.

My approach on a YZF would be to put the cooler in the return line. It runs through the ignition cover on an '06+, which would make it fairly easy to access, and leave the feed circuit un touched.

Gotcha! So from that point would you feed the oil up to the bottom of the left radiator to acustom made extension/oil cooler reservoir of the radiator, then back to the line that you rerouted it from? That's pretty much the way I've seen them on some of my buddy's Factory KTM off-road bikes.

Yes. If, for instance, we were working on an '05 instead, I'd just run the return line to the cooler, and the cooler outlet to the tank.

With one of the new ones, I envision tapping a fitting into the return passage at the bottom front drillway plug, then blocking off the passage out of the cover at the top, where it passes to the crankcase. That fitting I would run to the cooler. from there, I think there's room to tap into the crankcase next to the dip stick to complete the return circuit. If not, some variation of that could be done, it seems to me.

I understand. I don't know if I will actually go through all of the trouble or not, but I understand the idea. Thanks for your time.

gray - I see what you're saying - maybe they're getting better cooling because the radiators themselves are larger than stock? They definitely look thicker.

That would make sense.

Hey guys, new to this. I have a street legal YZ400F. Just bought a Trailtech Vapor & was reading your copmments about oil / coolant temp. Any ideas what the range of coolant temp should be min/max. I need to set the Vapor up with a max & a flashing 'idiot' light..thanks.

Coolant should not be allowed to boil. A 50/50 mix of ethylene glycol (the typical automotive green stuff) under 16 lbs. of pressure, as it is in your cooling system, boils at 265 degrees, F. That should be your max, but anything up to that is OK. YZF's don't have thermostats, so the temperature range is apt to be pretty wide compared with a system with one.

Other coolants boil at higher temps, and pure water boils at about 235-240 under 16 psi. Check the label of your favorite swill. Regardless of what miracle coolant you might use, remember that engine oil (in general) starts burning off, oxidizing, or suffering other forms of thermal degradation somewhere around 280.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now