Higher pressure radiator cap?


27 replies to this topic
  • twomancrew

Posted July 23, 2011 - 08:49 PM

#1

Bike has been overheating in the normal narly spots, but when it does over heat I would loss a large portion of my radiator fluid. Ordered higher pressure cap. Also ordered exhaust header gasket thinking sucking air could be causing over heating, not in yet. Recent changes to bike that might influence overheating are new OEM piston and rings (was 478 big bore) IMS 3.2g fuel tank (does it block air flow?), Revloc auto clutch ( Is it heating oil and causing over heating?)

OEM radiator cap 1.1 mb, new cap 2.0 mb. Will higher pressure cap cause problems? Pros, cons?

Other possible reasons for overheating? To lean? Ride at 8k' - 12k'. I think I have a 152 main jet.

  • DeeCee

Posted July 24, 2011 - 05:11 AM

#2

I take it the bike overheats at slow speeds which is normally due to low air flow over the radiators.

A higher rating pressure cap will alleviate the problem but not necessarily solve it. Also remember that the higher pressure cap will also result in the engine running hotter before it boils over.

What I suggest you consider is a catch tank so when the radiators do boil over, the fluid is caught in the catch tank, once your speed increases and the radiators cool off, the fluid is drawn back into the engine.

I ride hot desert all year round and have found the two best solutions are the catch tank mentioned above, and larger radiators.

  • Gunner354

Posted July 24, 2011 - 06:44 AM

#3

I take it the bike overheats at slow speeds which is normally due to low air flow over the radiators.

A higher rating pressure cap will alleviate the problem but not necessarily solve it. Also remember that the higher pressure cap will also result in the engine running hotter before it boils over.

What I suggest you consider is a catch tank so when the radiators do boil over, the fluid is caught in the catch tank, once your speed increases and the radiators cool off, the fluid is drawn back into the engine.

I ride hot desert all year round and have found the two best solutions are the catch tank mentioned above, and larger radiators.


You are saying a higher radiator cap will cause higher temps but you suggest a catch can to collect boiled coolant. The two scenarios are doing the same thing.
Boiling coolant into a recovery bottle will result in less in the engine thus causing higher engine temps.
I use Evans coolant which has a higher boiling point so it is nearly impossible to loose any coolant which makes the motor run hotter in some cases but if you are aware of that and then all is good. I would rather loose no coolant and not have a higher pressure in the system that's why I chose Evans. It just seems to be the easiest fix and works very well. Never have lost any coolant in some nasty scenarios and never had any engine problems.

Edited by Gunner354, July 24, 2011 - 08:51 AM.


  • ttr250dude

Posted July 24, 2011 - 12:12 PM

#4

Stock is 1.1 bar. Most guys wont go over 1.6 bar in fear of bursting coolant hoses. I would get a 1.6 bar if i were u. Alot of guys including myself like Engine Ice because it helps cool the bike better than most other coolants. Search around for the PC fan mod. It's basically putting a 90mm computer fan behind one of the radiators. If you get a fan that pulls enough air, you will never overheat again.

  • Gunner354

Posted July 24, 2011 - 09:31 PM

#5

Stock is 1.1 bar. Most guys wont go over 1.6 bar in fear of bursting coolant hoses. I would get a 1.6 bar if i were u. Alot of guys including myself like Engine Ice because it helps cool the bike better than most other coolants. Search around for the PC fan mod. It's basically putting a 90mm computer fan behind one of the radiators. If you get a fan that pulls enough air, you will never overheat again.


Why? Pretty much a waste of time and money.

  • ttr250dude

Posted July 24, 2011 - 10:12 PM

#6

Why? Pretty much a waste of time and money.


Why what? Why do the PC fan mod? I'm assuming you dont ride slow single track that causes boil over, nothing wrong with that. When riding in slow single track stuff there is often not enough air flowing through the radiators to keep the engine cool. With a PC fan behind a radiator that flows 100 cfm or more, there is enough air flowing through the radiators to keep the bike cool.

KTM sells a fan that goes behind the radiator for this exact purpose. From what i've read, the KTM accesory is the same exact thing as the PC fan mod except for the fact that it uses a fan better suited for off road use and it plugs somewhere into the wiring harness as apposed to a remote battery. The KTM one flows soo much air that if you are losing coolant you can pull to the side if the trail, leaving the bike running, and the air from the fan will bring the coolant down to safe temps. :smirk:

  • Gunner354

Posted July 25, 2011 - 07:02 AM

#7

Why what? Why do the PC fan mod? I'm assuming you dont ride slow single track that causes boil over, nothing wrong with that. When riding in slow single track stuff there is often not enough air flowing through the radiators to keep the engine cool. With a PC fan behind a radiator that flows 100 cfm or more, there is enough air flowing through the radiators to keep the bike cool.

KTM sells a fan that goes behind the radiator for this exact purpose. From what i've read, the KTM accesory is the same exact thing as the PC fan mod except for the fact that it uses a fan better suited for off road use and it plugs somewhere into the wiring harness as apposed to a remote battery. The KTM one flows soo much air that if you are losing coolant you can pull to the side if the trail, leaving the bike running, and the air from the fan will bring the coolant down to safe temps. :smirk:


I do ride slow tight single track and I use Evans coolant.

  • grayracer513

Posted July 25, 2011 - 07:02 AM

#8

Why? Pretty much a waste of time and money.

No such thing. A fan solves the problem by eliminating the cause: the lack of air over the radiators. Expensive coolants that raise the boiling point to near 400 degrees and catch tanks and so on only allow the system to tolerate being hotter than it should be.

  • rjcook450

Posted July 25, 2011 - 09:24 AM

#9

Is there a easy way to adapt ktm's rad. fan to a yz450?

  • ttr250dude

Posted July 25, 2011 - 09:25 AM

#10

Evans coolant doesnt fix the root issue of over heating. It only masks it by not boiling until it gets to a much higher temp. It doesnt actually keep the bike any cooler.

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  • ttr250dude

Posted July 25, 2011 - 09:29 AM

#11

Is there a easy way to adapt ktm's rad. fan to a yz450?


The KTM one bolts onto tabs on the radiator that our bikes dont have. The KTM fan is powered by the bike's electrical system, our bikes dont have enough output to power extra stuff like that. The way i have mine set up looks clean and unnoticeable with the damage to the rads. Probably took all of 30 minutes from start to finish.

  • rjcook450

Posted July 25, 2011 - 09:43 AM

#12

ok, guess i havent seen pictures of yours.

  • grayracer513

Posted July 25, 2011 - 09:52 AM

#13

Is there a easy way to adapt ktm's rad. fan to a yz450?

The KTM fan is probably at least 10 times as expensive as a simple 12v computer fan you might find about anywhere, for one thing. That, and the YZ450 offers no source of power to run it from, so you'd need a battery pack anyway. If you get clever, you can also set it up with a thermal switch on the upper hose so it will turn itself on when it's needed.

  • ttr250dude

Posted July 25, 2011 - 11:09 AM

#14

I took a few pictures just now. I'll post them up around 7 tonight.

  • ttr250dude

Posted July 25, 2011 - 11:14 AM

#15

To add to Gray's post about the cost; I believe the KTM one is $130 for everything. A computer fan that pulls 100cfm is right around $30 if I remember correctly. Even wither the cost of wires, connectors,and a battery, you're looking at less than half the cost from KTM.

  • ttr250dude

Posted July 25, 2011 - 04:28 PM

#16

Posted Image


I use velcro to hold the battery in place and put it behing the cables. You can see the connector here too.
Posted Image

  • NewMexican

Posted July 25, 2011 - 04:41 PM

#17

Nice pictures!

P/n's perhaps?

How exactly is it attached to the radiator? Could you put one of them on both sides?

PS: Most guys here at 5000ft use the high cap 1.6, since everything boils at a lower temp at altitude (less pressure)...

I tried the Evans and also am of the opinion it just allows things to run hotter, not really good long term...

Water wetter, and Engine Ice help somewhat too.

...but a 152 main?!?! Even for high elevation that seems lean to me! What are your complete jetting spec's?

  • zaxcar1

Posted July 25, 2011 - 06:34 PM

#18

can we also get some pic with the battery in also thanks

  • ttr250dude

Posted July 25, 2011 - 08:33 PM

#19

Nice pictures!

P/n's perhaps?

How exactly is it attached to the radiator? Could you put one of them on both sides?


No part numbers. We happened to have a 90 mm pc fan lying around so i used that but I should get one that has a higher cfm output. There are holes on each corner of the fan to screw it into the computer. I put zip ties through those holes and through the radiators. The zip ties were small enough to fit between the radiator slots and not distrupt anything. I could take the fan off and there would be no evidence of zip ties ever being there.
I think there is enough room for 2 but there's no use for it. A single fan that pulls enough cfm will do the job.

can we also get some pic with the battery in also thanks


I can get some more tomorrow and have them posted by 8.

  • ttr250dude

Posted July 26, 2011 - 04:31 PM

#20

I only have one battery right now. The other one was a cheap one and ~10 years old and started leaking battery acid one day when I put it on the charger :smirk: . Usually i have 2 mounted side by side. One battery will last ~2 hours when freshly fully charged but it's at the end of the battery life at that point. When I'm an hour or so into a race I'll stop for a few minutes to take a breather and plug in the other battery so the fan always spins at full speed. Sometimes I'll stop 2 or 3 times in a 2 hour race so I don't wear myself out. I'm not in it for blood or points, just fun :p

Posted Image





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