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Cooling Systems Cooling Systems - Radiators, Water Pumps, Fans, Coolant, etc.

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March 16th, 2008, 03:54 PM   #1
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still overheating

Well went for another ride to mount disapointment yesterday the bike ran great except blowing its top two or three times i installed two 120 mm fans behind the radiator guards (they are now both smashed ,altercation with some shrubbrey the question i want to ask is i have a 1.4 bar radiator cap on the bike is it worth me going to 1.6 or 1.8 to try it out. the bike over heats up big hills low speed,have bleed the cooling system and all the other tips have got off the website, any advice would be appreciated
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March 16th, 2008, 08:13 PM   #2
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Hi Pitt,

I have been running Evans coolant for several years now and have had good luck with it, and will not go back to regular coolant. Like you, I was having boil over problems in some of the more extreme riding conditions that I do, I can't put the KTM fan on my bike, and the computer fans don't take water & dirt too well.

I also have a friend of mine who rides a late model 525 EXC and has been running Evans for a couple of years now with great success.

The only thing about Evans is that you have to use your head when you're riding. In other words when you're in a tight spot and are slipping the clutch a whole bunch and are not moving forward at all, you will have to know when enough is enough and let the bike cool down for a while. I have also attached at thread from a while back about Evans and Mr. Lineaweavers input on the subject which provided excellent clarification.

With the Evans you end up having a very low pressure system because the coolant does not boil until 400 degree's @ 7psi. 7psi is something like .4bar I believe.

As the attached thread will explain, according to Dale Lineawearver's numbers, the "hard parts" or actual temperature of the engine parts is about 20 degree's hotter than with straight coolant. I have found this to be acceptable to the alternative, which is having the motor boil over and lose coolant during a race. The motor and the coolant may get pretty hot in extreme conditions, but, it stays in the cooling system and once you get going again it will cool the motor off. Whereas if you have regular coolant and you boil it out it's not going to be there to cool the motor off. And, you will now have a nice air pocket in the bleed off area.

This last summer I decided to switch back to conventional coolant on one of my trips up to the sierra's. Long story short after a hard ride down to Kernville from Kennedy meadows, I was wishing I had never even though about switching back to regular coolant from Evans. I boiled my bike really bad down in a canyon, and luckily there was a creek nearby as I was out of water. Had to strain the creek water through a bandana when I refilled the radiator. On the next trip up to KM, I was back with Evans and had no issues.

Two suggestions: When you are climbing big hills, and doing tight trails, try to keep the revs in the mid range and not lug it too much. This will help keep the coolant flowing faster through the system. Second, maybe you could find an 06 tank and then you could install the KTM radiator fan and your problems would be solved.

If you do decide to go with Evans, you want the NPGR coolant, it is a bit thinner viscosity and is intended for systems like ours. And, don't buy the "prep" fluid, you don't need it.

Just do the following:

#1 Drain your system completely of all coolant, do the best you can to get all the old coolant out.

#2. Refill your system with NPGR coolant as you normally would and then go for a 30 minute ride. Just long enough to get the system good and hot. The NPGR will absorb any r remaining water in the system. Let the bike cool down completely.

#3. Drain the Evans you put in into a clean container. Use a strainer or something to keep catch any dirt. I'll talk about this later.

#4. Refill your radiator with the Evans NPGR coolant from the container that you bought as you would normally refill your system. You are done with your bike at this point, and are now ready to go riding without boiling over.

#5. Now for the Evans that you took out of the motor, we'll call this the flush. You can do two things with this flush, you can dispose of it how you would normally dispose of coolant or you can can save it for flushing another system. Your bike system doesn't hold a whole lot so some would just find it easier to get rid of it.

However,if you are going to save it for flushing another system, which is what I do, here's what to do. Put this flush evans into a pan and heat it up to about 220F, use a thermometer to make sure about the temp. Keep it at this temp until you no longer see any bubbles forming on the bottom of the pan. Let this flush cool off and put it into a sealed container and save for later. You have now removed all the water from this flush and it's now ready to use as a flush.

Here's a previous thread discussing Evans: ... torder=asc

Evans Web site:

Dealer in Auz that carries Evans.

61-0-3-9735-5655 P
61-0-3-9735-5699 F

Hope this helps,

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March 16th, 2008, 09:55 PM   #3
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1st thing that you have too establish is if the cooling system with cap installed on the
radiator is capable to to holding 1.4 bar, for instance if your water pump seal is leaking
you are not going to hold pressure, loss of pressure = lower boiling temperature
my 04 450 was a constant boiler until i discovered that the nipple on the rad overflow
hose was interfering with ability of the rad cap to hold pressure once problem was
solved my buddies would boil before me
if you install a recovery reservoir you will increase the effectiveness of radiator
being that the rad is always full

later VIKING
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March 17th, 2008, 12:34 AM   #4
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before allllllll that you must check for headgasket failure!

start the bike and run with the cap off. if you have a continuous stream of bubbles heading towards the pour hole then you have a gasket gone!

i run a 1.8 bar cap. i'm sure you can find something down under but should you fail we have 'demon tweeks' in wrexham here in the UK.


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March 17th, 2008, 02:12 AM   #5
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You can get a cap off a 2008 KTM EXCR as they are 1.8, If you don't have a KTM dealer near by call us at Sutto's 02 47311173 and order one from our spares guys.
Best Regards
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March 17th, 2008, 03:42 AM   #6
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cheers guys for that info,i might try that evans that daleo is talking about and i will get the cap off an 08 exc i live five minutes drive from a dealer thanks smsc.
In answer toyour question taffy i have checked the head gasket theres no leaks there.
and that recovery reservoir sounds interesting thanks viking
Am just doing a crank case breather bypass at the moment and taking whats left of my computer fans and bent up radiator guards(slight massage with the martello should fix them)
Will keep you posted
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March 17th, 2008, 06:43 AM   #7
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Making sure the oil level is at the bottom of the sight glass, and no higher, seemed to really help my overheating issues. There is a factory bulletin on this out there somewhere.
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March 17th, 2008, 07:30 AM   #8
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Also make sure that the engine is jetted properly, and go easy on the clutch.
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March 17th, 2008, 09:52 AM   #9
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Originally Posted by Johnf3
Making sure the oil level is at the bottom of the sight glass, and no higher, seemed to really help my overheating issues. There is a factory bulletin on this out there somewhere.
I have it in my gallery on the first page second row right side.

Good job pointing this out, I had forgotten about it!!
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March 17th, 2008, 07:09 PM   #10
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Here are a few good links. It may take awhile to get through them. ... ght=#27277 ... pic&t=1263
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