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How many times have you seen the animated movie "Cars"? :)
That looks to be a nice ride. How do your lady friends or wife like it?

I installed a coolant recovery tank on my '55 Chevy pick-up in the winter of '79-'80 when I rebuilt its engine, after I hand Polished the top Brass radiator tank & steel valve cover. :)

Here is the Motion Pro universal coolant recovery kit,
I've never watched the full movie, just clips of it. My kids loved it. as for what my wife thinks of it, well, she tolerates my mechanical addictions! (several cars, two bikes, and I'm thinking of getting back into flying--but that may be a step too far for her). The Hornet cruises nicely at 70+ MPH, with that long-stroke 308 6-cylinder loafing along. It's even reasonably quiet, such that you can carry on a conversation at a normal volume, but it's not as wind-noise free as modern cars. New window seals would help, but new molded rubber gets expensive.

Thanks for the link, but I don't need a coolant recovery tank. The top tank of the radiator has more than enough volume to allow expansion without overflowing. "The part not added costs nothing, weighs nothing, and won't break."
 

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In our northern climates, a slightly entrained air cooling system can operate acceptably well on our dirt bikes or my '55 Chevy pick-up.
But now we both can realize that they could have operated 'Better' if we had re-filled them to the maximum before a hot days ride/drive.

The recovery bottle simply eliminates the need to 'top-off' the system to guarantee 100% efficiency, because it automatically keeps it 100% topped off.
If you care to remember, it was another rather simple (IMO) cooling system issue which 'broke the camels back' between Glenn at klr650 . net and myself.
My take away is that if the bike doesn't boil over, then coolant doesn't leave the rad - there is no "entrainment" and you don't need an overflow or to top up the rad.

The stock KLR system allows the convenience of not checking the level and as a safety so when/if overheated you don't dump slippery (and toxic) coolant on the ground.

.......so the bike doesn't NEED the overflow system to function at 100%, it simply makes life a bit easier.


Dave
 

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My view of the way it works is this:

If you have no overflow bottle and you completely fill the radiator, then the first time it gets hot enough to expand the coolant there will be some coolant that will leave the radiator. When the system cools, air will be drawn into the top of the radiator. Now you have a system that can expand and contract and nothing leaves or enters unless there is a more drastic heating event. However, that air in the top of the radiator can become mixed with the coolant and you wind up with very tiny bubbles in the coolant (air entrainment, a term I don't like. I like 'very tiny bubbles in the coolant'). That makes the coolant somewhat less efficient as it places less coolant in contact with hot surfaces.

If you do have an overflow bottle, then when the coolant expands it moves into the overflow. When it contracts it moves back. The system is completely full of coolant at all times, free of air bubbles, and works slightly more efficiently.

To be logically consistent, one cannot buy into the idea of a radiator bypass system (after all, the system is 'good enough' without it) and not buy into a radiator overflow system (because the system is 'good enough' without it). They both are the same caliber of improvement: modest, added parts, added weight, and another item to fail and need preventative maintenance. All of which is a specious argument, given their reliability and lack of complexity.
 
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My take away is that if the bike doesn't boil over, then coolant doesn't leave the rad - there is no "entrainment" and you don't need an overflow or to top up the rad.
Dave
Dave,
When you first filled the cooling systems on your non reservoir equipped race bikes, you filled them to the very top, I suspect. (Which you should do.)

After your first ride, their fluid level would be down x amount. That is the air space which then gets emulsified (entrained) into the entire cooling system during your subsequent rides with that type of system. Just because your bikes or cars didn't heat up to the point of blowing even more coolant out of the system on subsequent rides does not mean that they wouldn't have if the ambient air temp had been just another 5 -10 degrees higher.

The Gen 1 KLR650 radiator is nearly too small in hot climates, even with a recovery reservoir.
The larger Gen 2 KLR650 radiator might possibly perform adequately, even in hot climates, without a recovery reservoir.

I know that you understand & appreciate the benefits of the Thermo-Bob as to warm-up, why the resistance to appreciate the benefits of a reservoir for Cool-Down?

Tom just posted, I'll read some more.
 
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Ok,

- I do understand and appreciate the value of the overflow/coolant recovery system and wouldn't dream of removing it from my KLR's........but to be overly logical, I think the system is a "nice to have", "makes life easier", not a "need to have or your bike won't run properly" kinda thing. I guess I have a hard time believing that a state of the art offroad bike has a cooling system that isn't optimal because they wanted to avoid a pill bottle sized overflow and tube - I just checked a 2020 YZ250 and no tank.

- To Tom's point: If you have no overflow bottle and you completely fill the radiator, then the first time it gets hot enough to expand the coolant there will be some coolant that will leave the radiator. When the system cools, air will be drawn into the top of the radiator. Now you have a system that can expand and contract and nothing leaves or enters unless there is a more drastic heating event. However, that air in the top of the radiator can become mixed with the coolant and you wind up with very tiny bubbles in the coolant (air entrainment, a term I don't like. I like 'very tiny bubbles in the coolant'). That makes the coolant somewhat less efficient as it places less coolant in contact with hot surfaces. That all makes perfect sense though I'm unsure of a) the rate of expansion of coolant up to normal operating temperature and the resultant volume change and b) whether or not the amount of air left after 100.00% full becomes 99% full (or whatever the real number is) causes any measureable or significant decrease in cooling system performance. Maybe those race bike engineers make the rads 5% bigger to compensate?

I get the theory, I'm just going off of experience with several dozen bikes and cars that didn't have such a system, didn't puke coolant onto the ground and seemed to function just fine. In the case of the cars built in the '60's and '70's, it may be that they weren't optimal but I have a hard time believing that a state of the art race bike built last week wouldn't have an overflow if it made a significant difference to how the cooling system perforns........more maintenance and no concern for the environment (on an offroad, closed course race bike) are things they don't typically worry about though which is why I suspect THOSE issues are the reason the KLR has the overflow, not because of any significant cooling system performance benefits.

I'm happy to be proven wrong; just not sure if the theory and the reality of this topic match that well...


Dave
 

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Didn't Eli Tomac just suffer an over-heat DNF in a muddy outdoor MX race this season?
Remember Chad Reeds muddy Daytona SX DNF some years ago?

I have wondered just how much coolant is Pushed Out / LOST in the start gate. I've watched the coolant accumulate on my shop floor from a freshly filled MX bike, in the first few minutes of start up. That dis-placed coolant might could have been drawn back into the cooling system when hitting the water spray in the 1st big sippy hole, rather than sucking air into the system. Maybe.

Maybe the factory mechanics ought to install a coolant recovery bottle onto those MX & Enduro bikes, specifically for Mud Races? They are gonna' get heavier anyway. ;)

Yes I know that many mud race dnf's are due to clutch failure. But if the cylinder & head run cooler, the whole engine will run cooler. On the 4 strokes that becomes even more important, cooler oil to help cool the abused clutch components.
 

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I have never understood the size of the KLR overflow tank. I once looked into adpating a Neeenja tank but never went anywhere with the idea.
 

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I raced on an off since 1982......I recall the odd bike overheating in extreme situations back in the day (stuck in a mud bog, pushing, duck paddling, etc) , but I don't remember having any issues in the last 10 - 15 years or so that I raced.....may have more to do with increased skill (and speed) than cooling system improvements! LOL

My last race bike (2010 KTM300XCW) had the factory fill on the coolant the two years I raced it. Never once did it so much as drip on my shop floor, nor do I ever remember adding coolant to the bike though habits formed in decades prior made me check before every race.



Dave
 

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Maybe the factory mechanics ought to install a coolant recovery bottle onto those MX & Enduro bikes, specifically for Mud Races? They are gonna' get heavier anyway. ;)
I'd think that if it helped, they would. ;-) .....and if not them, then perhaps the professional race team mechanics would....


Dave
 

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My last race bike (2010 KTM300XCW) had the factory fill on the coolant the two years I raced it. Never once did it so much as drip on my shop floor, nor do I ever remember adding coolant to the bike though habits formed in decades prior made me check before every race.
Dave
Did you ever race in 95-105F temps or 30 minutes of UN-interrupted sticky mud, in the PNW??
 
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