Which rad cap?

[pscook]

I have a 1.2 bar radiator cap that has seen better days. My 300 was spitting and gurgling in 85* weather today (mild to moderate hill climbs), and I suspect the cap to be dodgy. If I walk into a KTM shop, what part number/model/year will get me a new cap? Also, what pressure (resistance?) is recommended? I understand that 1.8 bar is all of the rage among the orange crowd, is that recommended for our bikes?

 

[bowhunter007]

I have a 1.2 bar radiator cap that has seen better days. My 300 was spitting and gurgling in 85* weather today (mild to moderate hill climbs), and I suspect the cap to be dodgy. If I walk into a KTM shop, what part number/model/year will get me a new cap? Also, what pressure (resistance?) is recommended? I understand that 1.8 bar is all of the rage among the orange crowd, is that recommended for our bikes?

You should be able take the old cap...walk in and get a new one. If you never had a heat-up problem before, you don't have to have a higher pressure cap. The higher pressure cap simply helps raise the boiling point of the coolant. Myself...I stick with what's been working. Frequent removal of the cap, is good enough reason to swap it out, anyway. How do your radiators look(cooling fins straight, no mud, leaves, other gunk plugging the cooling area)? Surely your rads have to be in better shape than mine

 

[waycrazy]

I am using a 1.4 bar KTM cap .Seems to be working perfect.
KTM P/N 59035009000

 

[HenrikSchmidt]

The higher pressure cap simply helps raise the boiling point of the coolant.

WOW Can you do that
Revolutionary.. I would think that it needed ALOT higher pressure to alter the boilingpoint of coolant water??
I thought the higher pressure cap only worked as a safety valve..

 

[pscook]

My system is in good order, radiators straight(ish) and clear of debris, no problems other than the leaky cap. I have had issues losing water since I bought the bike, this was the first ride where the issues were obviously apparent. I was probably a bit lean, too, which I am sure didn't help. The rubber seal is a bit torn and worn, so I just want to replace the cap to eliminate any other avenues of failure.

 

[jostby]

WOW Can you do that
Revolutionary.. I would think that it needed ALOT higher pressure to alter the boilingpoint of coolant water??
I thought the higher pressure cap only worked as a safety valve..

boiling point of water without coolant at 1.2 bar is 104c (219deg). With 1.4 bar cap it's 109c (228deg)


Many on this forum prefer to run the 1.4 I've never had an issue with either of our bikes using the oem 1.2 caps and as you see it isn't a dramatic change anyhow. My guess is most that have installed the 1.4 cap would have seen their problems go away by just replacing the old one like for like.

 

[GMP]

1.4 bar KTM cap. FWIW, KTM made the rads for the pre '07 bikes. The caps still fit the newer rads.

KTMs tend to boil a lot easier than GGs, likely because they hold less coolant and there is less mass to the motor. I guess thats why those guys like the 1.8 bar cap.

 

[Leo]

look at this graphic. It will help you to have your conclusions.
http://www.endurohp.eng.br/mecanica/refrigeracao/temp.gif

Here the pressure is shown with different collors.
In the X axis there different ethylene glycol proportions
And then in the Y axis the temperatura with the fluid will boil

 

[Cruiser]

I just switched my KTM to the 1.8.. as its the 4stroke.. I've been running a 1.4 on my gg's since my 97 GG.. too easy to boil over with the 1.2 ,, even basic watercooled mowing equipment has a 1.3 cap.. in fact I carry two of these in my tool box to events in case of a cap failure.. I ran a John Deere 1.3 cap on my 03 250ec for almost a year before switching to the 1.4