Overheating

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kdxlnt
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Overheating

Post by kdxlnt »

My wife has had her 1990 KDX200 for over ten years. At times it's overheated, other times not at all. I recently replaced the stock coolant overflow tank with one that fits behind the number plate so I could keep track of when the bike is spitting up coolant. We were in the mountains recently, 80 deg. temps, ascending from 7000 to 8000 feet or so in about 45 minutes. The bike spit up about 500 cc's of coolant into the overflow tank. We stopped and let it cool, and it sucked it all back into the radiator. At the end of the day, however, when I checked the coolant level in the radiator, I found we had lost about 250 cc's. The bike has Devol radiator guards. I'm wondering if this has something to do with the overheating. We had dropped the needle one notch before going up there, and dropped the pilot size by 1 or 2. This loss of coolant at times is not uncommon when we're riding at 3000 ft with stock jetting, however. Any suggestions? Is this overheating typical of KDX200's? Any thoughts would be appreciated. The bike's also got a sizeable dent in the exhaust pipe near the exhaust manifold.
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Re: Overheating

Post by KarlP »

KDX'es are no more prone to overheating than any bike, certainly less than most.
Spitting coolant into the overflow tank is not really a sign of overheating, it is just doing what it is supposed to do. I could not find a spot for an overflow tank on my hybrid so it does not get one. I usually find my radiators are a little low on fluid, 1/2 to 3/4" or so. If I fill them back up cold, it will spit it out back to that level pretty soon.

Have you looked at your water pump impellor? I had one that was just eroded away. I did not realize how bad until I compared it to a new one.
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Slick_Nick
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Overheating

Post by Slick_Nick »

Something to think about, your overflow tank should AWLAYS have fluid in it, even when cold it should be about half full. The rade should be full to the top with an overflow tank.
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Re: Overheating

Post by kdxlnt »

I fill the radiator to the top on that bike. I haven't yet put fluid in the overflow tank, though. I haven't looked at the impeller in many years, but it's worth a shot. Does anyone make a more powerful one for this bike? I'm still wondering if the radiator guards have an effect. I would take them off for a test, but I'm afraid she'd bend them on the first tipover. Is there any brand of radiator guards that people are happy with?
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Julien D
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Overheating

Post by Julien D »

Slick_Nick wrote:Something to think about, your overflow tank should AWLAYS have fluid in it, even when cold it should be about half full. The rade should be full to the top with an overflow tank.
The overflow tanks on the E bikes are notorious for always being empty. It sloshes out while riding is the general consensus. You can add in there as much as you want, it will be empty at the end of the day. That being the case, you can always expect the rads to be slightly low.

Being that this overflow tank is now mounted behind the number tank, it'll be easier to see if it sloshes out I suppose. 250cc's is not a great deal of fluid. That much could have sloshed through the vent or been lost as steam.

This is not to say you don't have a problem. Obviously you know your own bikes better than we do. From your description, it sounds to me like normal function. If the bike is actually overheating, it will be noticeable in the way that it's running. It will lose power, and possibly even stall.
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Slick_Nick
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Post by Slick_Nick »

Where is the overflow on the E series? My 220 has it behind the right side panel. Never lose a drop.
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Re: Overheating

Post by Julien D »

It's behind the left rear side panel. And trust me, it stays empty. It's a pretty well discussed subject. Something about the way the vent line is routed. There have been some reports of improvement by heating and bending the vent outlet upwards, and routing the vent line over the upper subframe rail. I never bothered with it myself.
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canyncarvr
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Re: Overheating

Post by canyncarvr »

Anecdotal for sure, but I've read complaints for years about Devol guards causing heat problems. Not saying they do, but that the complaints exist.

You didn't mention radiator condition. Any reason for them not to be up to snuff? Bent..crunched, interior crud?

A faulty cap will do that. It will release coolant at a lower than spec pressure. Check the radiator neck..at the seat for the inner cap seal. If it's not in good shape, it will leak.


A leaking head gasket will do that, too.

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Overheating

Post by Slick_Nick »

I run the KX500 high pressure cap on my bike a well. Might want to try that. Will prevent boiling over.
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Overheating

Post by kdxlnt »

Canyncarver, thanks for the tip. I should try taking off the radiator guards before doing anything else. The problem is my wife crashes a lot and once the rads are bent it's hard to get them guards back on. If I find it's the radiator guards, I think I could cut out some of the material in front of the radiator and just use them for tipover protection. Nick, what year KX500 cap do you use? Do you know if it's a 1.4, 1.6, etc? That sounds like the easiest solution if it works. I don't think the coolant was escaping the catch tank. I left the stock catch tank installed with coolant up to the lower line, although it's not connected to the radiator. I've lost none of it.
Thanks to all for the suggestions.
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Overheating

Post by canyncarvr »

kdxlnt wrote:Canyncarver, thanks for the tip. I should try taking off the radiator guards before doing anything else. The problem is my wife crashes a lot and once the rads are bent it's hard to get them guards back on.
You could try some rad braces instead of the guards to see if the overheating symptoms change.

That would be a rather expensive test.

Used to be Devol made specific note that their guards were NOT braces. The Devol website now seems to be geared completely to selling stuff..not to much in the way of information.

Any strength added across the front should help the rads from getting squeezed..and a brace added to the back should help the rads from getting bent back.

The best setup is to protect from both types of damage...that AND from sticks getting rammed through the core(s).

I dunno...seems to me that even with braces AND guards, a radiator is pretty much a glass chin..and a dirtbike pretty much leads with it every time it goes down.

Good luck!

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Overheating

Post by Slick_Nick »

The KX500 cap I got was off eBay. It's stamped "outlaw racing". It's a 1.5Bar. I think all KX500 and KDX caps are interchangeable.
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Overheating

Post by kdxlnt »

Nick,
Thanks for the info on the cap. I'll certainly try it.
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Re: Overheating

Post by canyncarvr »

A 50% increase in pressure is significant!

From 14.6 to almost 22psi? :shock:

caveat emptor

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