crf450 is too hot

[crf450owns]

hey, i got a 2002 crf450 runs greatt barley any problems.. except it overheats wayy to much, it will start ppouring antifreeze out of the overflow hose. can someone explain this to mee, likee is there aything i can do about it?

 

[Ol'89r]

If it overheats while sitting on the stand idling, that's normal.

If it overheats while riding it, you have a coolant or water pump problem.

You have to have air flow through the radiators to keep the engine cool.

 

[XRpredator]

not sure about the Honda, but I know my KTM tells you right there on the radiator to not overfill or it will overflow. Gotta leave room for expansion, or have a coolant recovery tank.

 

[whenfoxforks-ruled]

A slipping clutch will get that bike hot in a hurry. No white smoke, bubbles in the radiator?

 

[Spokes574]

From a honda owner to another.
OK I had this problem as soon as I added a high compression piston. Typically these pistons create more heat.
My solution was:
30% water / 70% antifreeze
Drilled holes in the bottom of the front fender.

Problem fixed. If you have a high comp. piston that is the cause.
Yes if you leave a 4stroke bike on the stand sitting more than 1.5min idle it will get hot and spill out antifreeze.

Spokes572

 

[Rich Rohrich]

Unless you live in a place where it gets cold, there is no good reason to run anti-freeze. Straight distilled water will provide better heat transfer, and ultimately better cooling.

To the original poster, what are the circumstances that cause what you are seeing as overheating?

 

[crf450owns]

biohazard

bio hazard, well sometimes when it runs at an idle to warm up then ill take it up and down the street 5th gear then bring it back home and let it sit for less than 2 min it will start slowly pour antifreeze out of the overflow tube

 

[Rich Rohrich]

As 89r pointed out, you can't let it idle for long periods on the stand. Too much heat builds up that the radiator can't get rid of quickly. Hammering on it going down the street doesn't help things.

Fire it up, don't let it sit there idling just ride it EASY till it warms up, and then push it, would be better.

That said, you should still service the cooling system if you haven't done it in a while.

 

[whenfoxforks-ruled]

Rich, do the "colder" products in the cooling system actually work? All that idle time adds up to engine time. I would rather be riding it?

 

[Rich Rohrich]

Rich, do the "colder" products in the cooling system actually work?

Are you talking about BS like Engine Ice? No, they won't do anything special despite what the marketing jerkweeds at the company want you too believe. But they will make your wallet a lot lighter, so that may improve lap times. :whoa:

Products like Race Kool ( http://www.precisionautoresearch.com/RACING_CHEMISTRY/PAR14.htm ) are very useful, not so much from a "cooling" standpoint, as a health of the cooling system perspective.

The surfactant properties of Race Kool can reduce the surface tension of straight water and can provide some improvement in heat transfer similar to what "Water Wetter" does. For my money it's value comes more from it's ability to keep the cooling system clean, which goes a long way towards good heat transfer and cooling. That plus it's ability to change colors in the presence of combustion gases makes it a great early warning system that a head gasket is leaking.

I just run distilled water and Race Kool in my CRF480 using stock radiators and the stock water pump. My guess is, my CRF makes more power and generates more heat then most. ;)

I've run the same basic setup in big bore YZFs and CRFs for a years and been very happy with the results.

For really hot conditions I've found the Fluidyne aftermarket radiators to be a useful upgrade.

http://www.mxsouth.com/fluidyne/flu...d-components-power-flo-off-road-radiators.htm

 

[whenfoxforks-ruled]

Yeah I thought the genius in the ability to change colors via a combustion leak was outstanding! It mixed with distilled water, and has no gelling characteristics. Your earlier statement about the distilled water and ant-freeze left a little gray area with me, again. Thanks Rich! I hate gray areas! Heard from Dave lately? I see the need coming real soon.

 

[IndyMX]

For really hot conditions I've found the Fluidyne aftermarket radiators to be a useful upgrade.

http://www.mxsouth.com/fluidyne/flu...d-components-power-flo-off-road-radiators.htm

I was talking to a friend of mine who's an engineer at CR Racing (they make rad's for Nascar/Indycar).. He suggested that the thicker rad's like Fluidyne makes cause more problems than they solve. His reasoning was that since there was more surface area and more fluid capacity, you wouldn't actually have a cooler system, only it would take it longer to heat up and cool down.

His suggestion for me to get cooler temps was just what you said with the water.. So, since then I've been running H20 & Water Wetter. I see a lot less loss of coolant in the 450 now.

 

[Rich Rohrich]

I was talking to a friend of mine who's an engineer at CR Racing (they make rad's for Nascar/Indycar).. He suggested that the thicker rad's like Fluidyne makes cause more problems than they solve. His reasoning was that since there was more surface area and more fluid capacity, you wouldn't actually have a cooler system, only it would take it longer to heat up and cool down.

He may very well be correct. The bikes we've run the Fluidyne radiators on have seemed to show lower radiator surface temps taken with a non-contact heat gun. I don't have enough data measuring running water temp with the DAQ system back to back with the different radiators to dispute his theory. Maybe this spring I'll be able to fix that. ;)

 

[whenfoxforks-ruled]

All the big bore kits get bigger radiators than stock. That is the whole idea, bigger, more room? And they do not fold like an accordion when it falls over. Are all your fins straight, outer shell not tweaked? A pressure washer can fold the fins over. They make improved shrouds for more flow, drilling the number plate and front fender.Over heating can also be from running lean or a worn engine will run hot. How is the impeller? Hope it always had distilled water in it. And, what rpm does it idle at? Is it overheating, or just a bad radiator cap? Is it just puking out the excess from"topping it off"?

 

[IndyMX]

I also got one of them fancy Cycra vented fenders.. Love it!

 

[Matt90GT]

Hrm, thinking of that nascar idea just dont make complete sense to me.

If all you do is add larger capacity radiators, that allows more fluid in the system and also more surface area to disapate heat. With more fluid it will also take longer to cycle the complete system fluid thus it stay in the radiators longer allowing more time to cool.

$.02

 

[IndyMX]

Hrm, thinking of that nascar idea just dont make complete sense to me.

If all you do is add larger capacity radiators, that allows more fluid in the system and also more surface area to disapate heat. With more fluid it will also take longer to cycle the complete system fluid thus it stay in the radiators longer allowing more time to cool.

$.02

Except for one problem.. I should have mentioned this in the first post... Where the big issue comes in to account it that the rad's are thicker, which takes more to push the air thru, thus losing efficiency.

 

[XRpredator]

With more fluid it will also take longer to cycle the complete system fluid thus it stay in the radiators longer allowing more time to cool.

$.02

yet, it would also mean that the hot fluid would be staying in the engine longer, giving it more time to get even hotter, right?

€.11

 

[Spokes574]

I had my %'s flip flopped above
its 30% antifreeze 70% water.
Plus I add RedLine's water wetter.
Thanks for catching that Rich.

Spokes572

 

[Matt90GT]

yet, it would also mean that the hot fluid would be staying in the engine longer, giving it more time to get even hotter, right?

€.11

no because you have not increased any capacity in the engine. Just the radiators. Thus the fluid will have more time to stay in the radiators and pass the heat.

Yeah the trick to thicker radiators is in the fins. They are not as plentiful as the standard size radiators thus allow equivalent airflow through them. So same speed, you will have more surface area to disapate the heat and more coolant there which will have more time before it has to get cycled back into the motor.

Lots of variables there! That is the key I believe! Fin density, size and keeping the same waterpump speed.

 

[IndyMX]

Huh.. the Fluidynes a friend of mine had on his KX450F were the save width and whatnot of the stockers. Just thicker. Otherwise they weren't any different.

 

[whenfoxforks-ruled]

Track talk as best I remember. The overbores ran hot on oem rads. Fluidyne seemingly solved the problem. Without an actual temperature sensor in the system? Then its guy figuring time, gray area. An impeller for more flow, but to what end? Now fluidyne's and a higher flow impeller? How about the bikes with cooling fans? Do they all require a battery? All 450's do not have this problem, his is like an 02? Has the impeller been checked for wear, erosion from fluids? Some guy could have put some engine ice and tap water in there at one time. That gel it forms is a tuff one to clean out? Have you tried flushing/cleaning the cooling system?

 

[James]

Are you talking about BS like Engine Ice? No, they won't do anything special despite what the marketing jerkweeds at the company want you too believe. But they will make your wallet a lot lighter, so that may improve lap times. :whoa:

Quoted for emphasis.

 

[asfaultdemon]

So id like to add to this even tho its old . The stuff about adding strait water to the cooling system is not a smart thing to do. Antifreeze is not just a coolant it is also lube for the water pump same as in cars. This is why it has a greasy feel to it. Without it the water will distroy the bearings. Just a fact to concider when reading what is posted that it might not be the truth you should research it yourself before taking anyones word for it.