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CRF450R Overheating?

By MMH,
in CRF450R/RS/RWE & RX

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Proficient

MMH

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How do I know? If I let it idle for more than a couple of minutes it starts pushing coolant down the tube. I'm worried that when on slower trails I will run low on coolant, overheat the engine & not know it. So how do I know when the CRF is too hot?

Also, Will an exansion tank from a 250X or 450X help?

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Apprentice

c_bach_115

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Depending on how your skid plates mounts you can use the overflow tank from a 450x. I have an 05 CRF-450R and I was able to use the overflow tank from a 450x. With the tank installed, I was only able to use 3 of the 4 mounting brackets for my skid plate. I safety wired the one where I couldn't use a bracket(it was the front left corner). I have ran several hare scramble races and haven't had an issie with losing all my coolant since I installed the tank. Just letting you know that you can use the tank from a 450X as long as you can still mount your skid plate.

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Explorer

Masterlink52

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There are various trick or gimmicks to try and stop the coolant from escaping and some of these may be affective but the facts are the CRF450R is not designed to be a trail or tight terrain bike or designed to run at slower speeds, they are race machines therefore require consistent air flow thru the radiators.

I agree “Engine Ice” coolant helps but if the radiators do not maintain a consistent air flow passing through them it doesn’t matter what type of coolant used the motor gets hot and the radiators will percolate coolant out the overflow hose depleting coolant level and if not monitored will overheat the engine. I’ve personally have never overheated a bike engine, but if you do be certain the engine will quickly let you know in one way or the other and it could result in major $.:eek:

It's no secret that the CRF450X is designed for off road trails etc and comes with electric start, front/rear lights and the benefit of a radiator overflow reservoir to eliminate loss of radiator fluid and over heating. ?

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Experienced

nexrace

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Dude do a search on "turkey baster". It is a great overflow device. People have also on the early bikes made overflows out of their frame spars. You can do a search on this for some helpful info. If all this back yard tech is no good for you check out motion pro for an overflow. Another good idea is the 250x over with a couple of tabs added to your sub frame.

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Grand Master

sonobob

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My '06 would puke coolant in the slow stuff until I made two small changes...I keep the coolant level filled to the tops of the fins inside the radiator, and I added a few ounces of the Redline Water Wetter. It not only keeps the engine temps down but also lubricates the water pump seals and helps prevent rust/corrosion in the system. ?

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Newbie

flyingbryan

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I have the same problem with overheating and I tried the Fluidyne radiators on my 02 CRF450R. With the new radiators on I had to take off the Devol radiator guards (not good). No luck at all with the Fluidyne's, but I think I have other problems because I can only ride for about 20 minutes before all the fluid is gone out the overflow line. I put a water bottle on the overflow to confirm that is where the fluid is going. The first year or two I had this bike I never had this problem with overheating. Anyone have any idea's? Maybe the water pump?

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Enthusiast

oldshooltoy

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I have the same problem with overheating and I tried the Fluidyne radiators on my 02 CRF450R. With the new radiators on I had to take off the Devol radiator guards (not good). No luck at all with the Fluidyne's, but I think I have other problems because I can only ride for about 20 minutes before all the fluid is gone out the overflow line. I put a water bottle on the overflow to confirm that is where the fluid is going. The first year or two I had this bike I never had this problem with overheating. Anyone have any idea's? Maybe the water pump?
blown head gasket? do a block test
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Community Regular

thrillbillie56

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I have the same problem with overheating and I tried the Fluidyne radiators on my 02 CRF450R. With the new radiators on I had to take off the Devol radiator guards (not good). No luck at all with the Fluidyne's, but I think I have other problems because I can only ride for about 20 minutes before all the fluid is gone out the overflow line. I put a water bottle on the overflow to confirm that is where the fluid is going. The first year or two I had this bike I never had this problem with overheating. Anyone have any idea's? Maybe the water pump?

I had that problem(although not quite that severe) and it turned out to be that my radiator cap was bad, so i replaced it with a higher pressure one, and it has worked fine ever since. Or if that doesn't work it could be the water pump, pull it apart and check the seals/impeller. And if that is not the problem, check the head gasket, it is possible due to the age(if its never been replaced) of the bike that the old one is trashed...you can do this by doing a compession test, or pulling the head if you feel the need to do so(good time to check the valves too)?

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Newbie

flyingbryan

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Thanks for all the help on my 02 450 overheating problems. I will have some time off work next week to try to get the problem fixed. I will let you know how it goes.

Thanks again,

Bryan

I went riding this weekend and found the problem with the overheating. It was the Fluidyne Radiator. When putting on the cap one time it was a little hard to get on so I started looking at the area around the cap and saw the overflow nipple had the threads in just far enough to interfere with the cap. I took out the nipple cut the threads back, put it back in and the overheating problem was gone. I also put in the Boyesen Hy-flow water pump over the weekend along with new Engine Ice coolant. With all this I could not get the bike to over heat on trails, or hill climbs in 100 degrees F weather. What a difference a day makes. I also had a home made overflow bottle on to see if, and when any fluid was coming out. There was the smallest amount that would come out and get sucked back in after moving again but I don't think it is necessary to have the overflow bottle.

One note for anyone with the overheating problems. The time you get the fluid coming out the overflow is after you have been on the gas and you go to idle, and if you stay at idle sitting still.

I was riding with some newer guys on trails (slow), stop and go, and at idle after hard riding, and keeping it at idle for 5 minute or more before going and never had it overheat after the fix.

Thanks to everyone with the help, now I can get back out there and ride.

Bryan

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Just thinkin

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This is going to take a bit but read on.

There is a difference between overheating & spiting water out of the overflow.

A cooling system requires PRESSURE to raise the boiling point of water, which happens to transfer heat better than any other coolant, all the "snake oil" included. The pressure is created when the fluid heats up & expands. Since water, or any other fluid expands when heated, the expansion in the enclosed space creates pressure in this enclosed space. This pressure raises the boiling point of the coolant and is an absolute necessity. Try filling a can to the top with water, closing the top, & putting it on your kitchen stove. It BLOWES UP as the fluid expands with no place to go !

The radiator cap is a crude pressure relief valve that prevents over pressurization by dumping the excessive pressure. Unfortunately, a rad cap does not regulate the pressure, it DUMPS it ALL! As soon as your cap dumps water, because of the natural expansion of the coolant, you have eliminated your means of producing the needed pressure. The coolant has already expanded so it has lost its ability to re-create the needed (expansion) pressure! What has happened is you have lost the pressure and along with it the ability to regain this needed pressure/boiling point! It's all downhill from here.

The key is to never allow the expanding coolant to open the cap ! You accomplish this by maintaining an "air spring" (air compresses & fluid doesn't) between the level of the coolant when hot & the radiator cap. This means letting the system find it's natural level by a one time overfill, then reducing the "cold level" of the coolant slightly below that level. Do not fill between rides because the level has been reduce to the top of the radiator tubes when cold ! Be assured, when up to operating temp the system will be full!

There are coolants that have a higher boiling point than water. However, they give a false sense of security because the don't "spit out" the overflow tube". Expansion, and the ability to transfer heat, are two totally different things. Use distilled water, water pump lube, and the highest rated pressure cap (1.9) you can get your hands on. Don't overfill your system & your bike will be happy. Don't forget to use anti-freeze during the winter when cooling isn't a problem.

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  • 1 year later...
Experienced

nexrace

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I know this is a way old thread but for some reason I got caught reading it....

In the past I sourced a rad cap from a ford escort which is high pressure & waay cheaper in price than what is currently available for dirtbikes. Try napa with your spec on the diameter of the tabs on the rad cap & save some money...dan

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