radiator cap

[Charlie500]

What is the stock radiator cap pressure? I just ordered an after market one that is 30 lbs. Is that right?

[flyingfitz]

I think most caps are around 16 psi or 1.1 bar.  I bought a 1.6 bar or around 23 psi. It works great. 

Fitz

[bob larry]

I flipped through the manual but didnt see stock.  Would like to know too

 

[Danger4u2]

Part numbers for a 2004 KX500
Stock part # 49085- 1070  1.1 bar or 15.95415 psi
Optional part # 49085- 1073  1.6 bar or 23.20603 psi

1 bar = 14.5037738 pounds per square inch
1 bar is atmospheric pressure at sea level

[maddoggy]

flyingfitz is right, 1.1 bar = 15.95 psi is the stock cap rating. the optional cap is rated at 1.6 bar = 23.20 psi. anyone that rides their k5 hard will want to run the 1.6 bar cap due to the potential to overheat. the higher pressure cap will keep the coolant where it belongs. if you are running the high psi cap and still overflowing coolant you may have a head leak issue or some other problem.

looks like danger snuck one in under me while i was typing

[Danger4u2]

By going to the 1.6 bar cap you are increasing the pressure by more than 1/3 over stock, 7.25 more psi total.
I would break loose and retighten all the hose clamps.  Don't get out on the trail and find they were tight enough for 15.9 psi but not tight enough for 23.2 psi.  It could be a long push back to camp.  Most of the areas we ride you could not push a bike out.  Not getting burned by radiator fluid should be a concern also.

[maddoggy]

By going to the 1.6 bar cap you are increasing the pressure by more than 1/3 over stock, 7.25 more psi total.
I would break loose and retighten all the hose clamps.  Don't get out on the trail and find they were tight enough for 15.9 psi but not tight enough for 23.2 psi.  It could be a long push back to camp.  Most of the areas we ride you could not push a bike out.  Not getting burned by radiator fluid should be a concern also.

thats some good advise danger4u2!

[Danger4u2]

I think the tank would protect the family jewels if a hose blows off.

[Motorrad]

Yikes thats alot of pressure.... My rule of thumb has always been to run the least amount you can get away with... easyer on all the cooling system...

[maddoggy]

if you ride a k5 to its limits like dune riding forces you to do, you cannot get away with running a stock cap.  i learned the hard way. now i run the optional high psi cap.

[Motorrad]

if you ride a k5 to its limits like dune riding forces you to do, you cannot get away with running a stock cap.  i learned the hard way. now i run the optional high psi cap.

Hmm.. Only time I ever had a problem was when I was running a Knobby one trip... high revs all the time got her hot.

[Dutch-K5 Fan]

MXA says that 1.6 is the most to use on stock radiators. Factory teams use a 1.8 or maybe even more
these days(seen a 2.4 once). The idea of more pressure is, it's better to get hotter cooland.
Than air when boiling so a hole can melt in the head.

Since 2004 (rmz 250) I've only use a 1.6 cap. Even on my AF for 1.5 years now. Better save than sorry.



Dutchie

[Charlie500]

So the one I bought on eBay says its 30 lbs...... that could cause some problems...

[Danger4u2]

30 psi (2 bar) would be twice the pressure of a stock cap.  I have never had a problem with the stock cap.

[kaw rider]

you what to run as high pressue as possible. if your cooling is is right, you can get by with a 16 psi cap. cool running motor is free hp.