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Benefits of high pressure radiator cap?

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So I rode in an organized Pennsylvania dual sport ride two weekends ago (7 Mountains) and for the last half hour I was being tortured in some real slow, very rocky terrain.  Got the crap kicked out of me.  The temp readout on my TTO gauge reached 275 degrees, which is the most I've ever seen it at.  This is even with a new right-side Myler's radiator and Engine Ice, but with no radiator fan.

I'm not particularly concerned because the bike (2016 390RR) did not overheat or puke out any coolant and as soon as I got out of the slow rocky stuff and got some speed and airflow going she cooled right back down to around 150-175, which is the typical operating temperature range that I experience when I'm moving along.  Overall, the bike ran like a champ for the entire 105-mile ride with no issues whatsover. 

So my question is would a high pressure radiator cap such as the Myler's or the CV4 benefit me in any way?  Would the engine temps not get as high?  Again, I'm not overly concerned because the above scenario only represents a small percentage of the type of riding that I do.  My outings usually consist of anywhere from 50-120 miles with maybe around 5-7% of that being tight, slow technical stuff where I can expect engine temps to get pretty high. 

Anyone running one of these caps with good results? 

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A higher pressure/bar radiator cap does only one thing: it raises the boiling point temperature of the coolant, by increasing the pressure inside the radiator.

It does not change anything else.

It exists to prevent (reduce the occurance) of boiling coolant/overflow of coolant.  It allows the water to get hotter  before boiling.

The only way to lower your temps is to move more water and more air at the same time: fan and pump impeller and or larger radiator.

If you are not overheating the coolant to overflow, then you don't need to do anything.

Water temps don't mean much unless they are sustained for hours.

It is common for extreme riders to get coolant up to 275 every ride....

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I think it would be better to get an overflow tank if your bike does get hot at some time in the future. So if it boils out it comes back in later. It's a simple and cheap mod too and better than just a high pressure cap. 

If you don't need more mods no big deal. For me I just get a fan, hp rad cap,overflow tank just to start and decide to go from there.. That's all my bikes..But with 4 strokes especially since they run hotter.

Edited by hawaiidirtrider
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I would just put a fan kit on it. My ktm runs hot in the tight stuff. I have it dual wired to a thermo switch and a manual switch so even if the thermo switch doesn't kick it on I can manually turn it on for peace of mind.

Edited by randysoo
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I would just put a fan kit on it. My ktm runs hot in the tight stuff. I have it dual wired to a thermo switch and a manual switch so even if the thermo switch doesn't kick it on I can manually turn it on for peace of mind.


If you add a fan check the output of your stator.
I added a fan and with the stock headlight it killed the battery first time out.
I upgraded the stator to 150 watts.

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I just got the fan kit from Beta for my 3 Betas.. I guess they figured it all out already. Later I've upgraded my stator for light options later for 2 bikes..but just haven't installed good lights yet. I guess I'll get an upgraded stator for my 300 at some time.. just for big lights for future night rides.

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Thanks guys for the replies.

I had the Beta factory fan on my stock radiator but when I crashed the fan got damaged.  After upgrading to the Myler's radiator I decided to hold off on the fan because I thought my bike ran on the cool side to begin with, and the fan rarely kicked on anyway.  The 275 temps are on the rare side for me. 

I will monitor in the future and if I start hitting higher temps regularly then I will consider buying another fan and installing.  

djl2014 - It doesn't sound normal that adding a fan would kill the battery.  Why would that happen?  I didn't have any issues when running my fan and stock headlight. 

Edited by Ocaptainmycaptain
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2 hours ago, Ocaptainmycaptain said:

Thanks guys for the replies.

I had the Beta factory fan on my stock radiator but when I crashed the fan got damaged.  After upgrading to the Myler's radiator I decided to hold off on the fan because I thought my bike ran on the cool side to begin with, and the fan rarely kicked on anyway.  The 275 temps are on the rare side for me. 

I will monitor in the future and if I start hitting higher temps regularly then I will consider buying another fan and installing.  

djl2014 - It doesn't sound normal that adding a fan would kill the battery.  Why would that happen?  I didn't have any issues when running my fan and stock headlight. 

...because your charging system stops working below a certian rpm and mph, so when the fan starts working, which is usually in low mph, the battery load is higher from the fan, and it drains the battery.... that is why so many KTM guys (no kick starter)  put switches on their fan, just in case, so the estart continues to work. 

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What Krannie said...

Also the stock headlight was always on (RS street legal) and draws 55/65 watts. Fan draws 35 watts. Stock stator is 100 watts.
I installed a light switch and a LED bulb that draws 30 watts.

Haven't had to kick start my bike since.

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51 minutes ago, djl2014 said:

What Krannie said...

Also the stock headlight was always on (RS street legal) and draws 55/65 watts. Fan draws 35 watts. Stock stator is 100 watts.
I installed a light switch and a LED bulb that draws 30 watts.

Haven't had to kick start my bike since.
 

Oh yeah, you gotta switch your lighting on and off....my switch turns off everything but the rear brake light (but turns off the running light)

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Not sure about the stock split AC/DC systems charging volts. I already knew how quickly batteries die with the stock systems. I ended up going with a 100 watt rewound stator and adjustable DC regulator. Mine is set at about 13.8 volts at idle with light and fan running. 

If you go with this setup you will not have to worry about draining the battery. If you decide to use heated grips then upgrade then you can rewind up to 150 watts using stock ignition cover. 

2 hours ago, djl2014 said:

What Krannie said...

Also the stock headlight was always on (RS street legal) and draws 55/65 watts. Fan draws 35 watts. Stock stator is 100 watts.
I installed a light switch and a LED bulb that draws 30 watts.

Haven't had to kick start my bike since.
 

Sorry but your stock stator has an output of about 55 watts DC and 30 watts AC. The AC watts are converted to DC using a rectifier. When using both fan and headlight your battery is draining with the OEM system. Some guys think it's slick to convert to DC by floating the stator ground. Sadly the stock charging system just cannot keep up unless lights or fan are turned off. 

As far as the high pressure cap, I decided to run Evans many seasons ago on both my bikes. I can get the temps to over 300 degrees and open up my cap with almost zero pressure. I do use a 2.0 bar/30 psi cap. This is in the event I need to use water in an emergency. For you I would say yes get the high pressure cap just for piece of mind as well as an overflow bottle.

If you're running Mylers radiators just get a OEM KX65 cap for cheap. It's rated at 1.8 bar which is a nice upgrade from stock. For overflow protection a KDX200 overflow bottle is cheap, durable and will mount almost anywhere. Motion Pro one is also nice but harder to find a good mounting solution.

For a cheap fan just get a Spal 30103018 4" Paddle Blade Puller Fan for around 60 bucks and zip tie it to radiator. Very low profile and super durable. 

Mine is still holding up (over 100hrs) with cheap Home Depot zip ties:

IMG_0990.thumb.jpg.617d6d023b158e5278d806c06d6d490f.jpgIMG_0993.JPG.01cb5c949174eed9db70a31f7ead311e.JPG

 

 

Edited by ballisticexchris
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Not sure about the stock split AC/DC systems charging volts. I already knew how quickly batteries die with the stock systems. I ended up going with a 100 watt rewound stator and adjustable DC regulator. Mine is set at about 13.8 volts at idle with light and fan running. 


Sorry but your stock stator has an output of about 55 watts DC and 30 watts AC. The AC watts are converted to DC using a rectifier. When using both fan and headlight your battery is draining with the OEM system. Some guys think it's slick to convert to DC by floating the stator ground. Sadly the stock charging system just cannot keep up unless lights or fan are turned off. 

 


Yep, you are correct about the stock stator.
I picked up a 100 watt stator from Dave at get dirty dirt bikes.
Also a fan kit, his are plug and play.
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17 hours ago, Ocaptainmycaptain said:

Thanks guys for the replies.

I had the Beta factory fan on my stock radiator but when I crashed the fan got damaged.  After upgrading to the Myler's radiator I decided to hold off on the fan because I thought my bike ran on the cool side to begin with, and the fan rarely kicked on anyway.  The 275 temps are on the rare side for me. 

I will monitor in the future and if I start hitting higher temps regularly then I will consider buying another fan and installing.  

djl2014 - It doesn't sound normal that adding a fan would kill the battery.  Why would that happen?  I didn't have any issues when running my fan and stock headlight. 

100% agree that a stator change should not be needed to add the fan. My 15' 350 has been fine with the fan added, and it runs a fair amount here in Texas, and I have a lower temp switch in mine too. Just the replacement battery from Beta (the yellow one, forget the name, NOT a Shoria or similar Lithium hype) And all is fine.

Back to OP...I have stock cap, stock rads, Unabiker guards, Beta fan, and now billet impellar, but even before the impellar, this bike has never puked an ounce of coolant unlike the pumpkin pals that I ride with. I smell them all the time...seriously. We ride a ton of 1st-3rd single track here in Texas.

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38 minutes ago, djl2014 said:

 


Yep, you are correct about the stock stator.
I picked up a 100 watt stator from Dave at get dirty dirt bikes.
Also a fan kit, his are plug and play.

 

Very cool! Yes the new fan kits are really sweet. He didn't have them when I got mine. Best of all they come with a nice fin sensor and gauge:

http://shop.getdirtydirtbikes.com/Universal-Fan-Kit-665-7322.htm

 

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Thanks again guys for all the replies.  Like I said, I'm going to keep an eye on my temps over the next couple of rides and see if I notice anything unusual.  Maybe consider adding on one of the universal fan kits from Trailtech in the future. 

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21 hours ago, vwprostock said:

100% agree that a stator change should not be needed to add the fan. My 15' 350 has been fine with the fan added, and it runs a fair amount here in Texas, and I have a lower temp switch in mine too. Just the replacement battery from Beta (the yellow one, forget the name, NOT a Shoria or similar Lithium hype) And all is fine.

Back to OP...I have stock cap, stock rads, Unabiker guards, Beta fan, and now billet impellar, but even before the impellar, this bike has never puked an ounce of coolant unlike the pumpkin pals that I ride with. I smell them all the time...seriously. We ride a ton of 1st-3rd single track here in Texas.

Do you notice any difference in engine temps with the billet impeller?  Which one do you have?  Are they straightforward to install?

I see motosupply.com has the Boano one for $83.  I'd consider adding that first before putting on another fan.

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25 minutes ago, Ocaptainmycaptain said:

Do you notice any difference in engine temps with the billet impeller?  Which one do you have?  Are they straightforward to install?

I see motosupply.com has the Boano one for $83.  I'd consider adding that first before putting on another fan.

I am putting one on my 430 this weekend, but due to a shoulder-meets-tree incident, I will not be testing it out. 

I am going OS impeller, overflow bottle, 2.0 cap, and no fan. That should keep the liquid inside.

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2 hours ago, Ocaptainmycaptain said:

Do you notice any difference in engine temps with the billet impeller?  Which one do you have?  Are they straightforward to install?

I see motosupply.com has the Boano one for $83.  I'd consider adding that first before putting on another fan.

Not really...but also do not have a temp gage of any kind. I cannot imagine a 2nd fan being needed...maybe on a 480/500, but not my 350. The fan made the biggest difference, and all I was trying to fix when I put it on was a fairly serious loss of throttle response when it was way hot. Seems to me there is a missed mapping point/window on the EFI at high coolant temps. Once I put the fan on it cured that 90%, and then when I changed the switch to a tad lower temp, I have not noticed it again.

I only honestly put the impeller in because I was going in that side of the engine for oil pump gears, clutch plates, etc and figured awe hell...put the impeller in.

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17 hours ago, Ocaptainmycaptain said:

Do you notice any difference in engine temps with the billet impeller?  Which one do you have?  Are they straightforward to install?

I see motosupply.com has the Boano one for $83.  I'd consider adding that first before putting on another fan.

My buddy put an impeller on his 250 rr and he says he thinks it's a good difference . I'm going to put one on as time goes on . Lots of terrain that overheats bikes here. I'm good now but cooler is better . Got a fan and overflow tank and hp cap. Big rads and the impeller will go on later. I'm keeping this bike a long time

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1 hour ago, hawaiidirtrider said:

My buddy put an impeller on his 250 rr and he says he thinks it's a good difference . I'm going to put one on as time goes on . Lots of terrain that overheats bikes here. I'm good now but cooler is better . Got a fan and overflow tank and hp cap. Big rads and the impeller will go on later. I'm keeping this bike a long time

And as an added bonus you don't have to worry about the OEM plastic impeller coming apart!

IMG_1807.JPG.fb78c8e29af8284c2e185673865e1f16.JPGIMG_1808.JPG.ed483fc98f420aae14a663af4f922dbe.JPG

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