Overheated and ran out of coolant????

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GregS
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Overheated and ran out of coolant????

Post by GregS »

After a very long and steep climb, with tons of stalling, high-revving, and clutch feathering (or trying to feather), I arrived at the top with my KDX200 blowing steam and the fluid in the coolant reserve tank literally boiling -- and I mean a rolling boil. You could see and hear all the gurgling going on. I then let it rest a while as I walked a ways back down to help some friends get up. I actually ended up riding my friend's XR250 up the last tough section.

First: man was that XR250 easy to ride up in comparison! It required no clutch feathering at all -- just tractored right up @ very low rpms. Sure - the KDX is more flickable in the flatter trails, but I sure am wishing I could have that XR engine in my frame! I'm not into speed that much, so maybe the 2 strokes finer qualities are lost on me.

Second (and most important): After resting and eating lunch, we headed out over much flatter (or gently rolling terrain). I stopped for a bit and noticed my reserve tank was completely empty! I thought, "holy cow -- am I about to trash the bike -- running it with little or no coolant?". So I filled up the reserve with drinking water from my camel back and took it easy on the way home. The engine seemed to run fine.

Since the water wasn't distilled, I'm going to flush the system today. But I just wanted to get your feedback: did I do the right thing? The KDX is new to me -- as are water cooled trail bikes. After reading the manual today to figure out how to flush the system I was wondering if there was still plenty of coolant in the radiator and I could've ridden back without using my drinking water.

Thoughts?

Third: I just realized that XR250 is air/oil cooled. Another enticement back to the 4 stroke world -- oh why does the KDX have to be so much more flickable! ;^)
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Indawoods
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Post by Indawoods »

Example:

You race your buddy and wipe him all over the place. Right?

Why is that you say? Gearing for one... nature of the design for another.

Your buddies XR is not a current design marvel but one of older days. It is a bulletproof design and if his overheated it would just die...right there without warning... maybe a little pinging but that's it.

I think you would benefit from a shorter gear.... a 12T countersprocket or 50 tooth sprocket. Also... what elevation are you riding at? How are you jetted? What fuel are you running.... Hell... what do you have?

We need a lot more information to be able to help you with this.... but you may have just been in too tall a gear... had bad tires... or just bad technique.

Your KDX needs modified to be the machine it can be... so if your running a bone stock KDX then I can believe you had these issues. But.... you do have to keep in mind it is a 2 stroke... the closest thing you will find to a 4 stroke but a 2 stroke never the less. And when you want to scream.... no XR 250 is going to give you that thrill. :supz:
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Post by GregS »

Hell... what do you have?
Very good question! More info would help...

'01 kdx 200
Gnarly Torque Pipe, FMF turbine core II silencer (just repacked)
Jetting: pilot 42, main 152 (down from a 45/155 combo), needle in 2nd clip from top.
elevation: this was between 3000 and 5300 feet
gearing: stock front, 50 or 51 rear.
Technique: oh, mine sucks, I can assure of you that
40:1 mixture, Mobil1 mx2t
Gas: premium.
Tires: new, running 10lbs front, 13 rear.

On general inclines, I've been impressed with how tractable the KDX seemed after hearing so much talk of 2 strokes requiring revving. This hill however was longer and tougher than I've ridden in my 4 outings to date on the KDX.

Still, my main question is the coolant issue: was my approach right? After realizing my reservoir was bone dry, I filled it with drinking water vs. risking running the whole system dry?
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Indawoods
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Post by Indawoods »

Get RB'd!

I did and at the second sweet spot... you cannot tell the difference between your KDX and a 4 stroke.

Your setup sound good!

On to the overheating.... Change to a different coolant. Waterwetter or some such coolant. Riding high elevations, you are going to run alot hotter than me at 600'... I have never had an issue and I run Peak 50/50 premix.

After the thing cooled down... you shoulda popped the radiator cap and checked the level... in the wild you have to do what you have to do... don't feel bad about it!I alway carry extra at the truck just in case so I don't have to use mineralized water. You can generally get by with little coolant to get back to camp if your easy on her...
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"People ate cows a thousand years ago for the same reason we eat them now. Cause they are easy to catch.We're not savages,we're just lazy. A cheetah could taste like chocolate heroin. But will never know. Those bastards are fast!!! "
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Post by KDXGarage »

Hi. Did you check your coolant level when you were on the trail by opening the radiator cap and looking in there or just by the coolant reserve tank level?

At higher elevations, it is easier to get it to boil over.

For better traction compared to the XR, you could put an equivalent quantity of lead on your bike to make it as heavy as his bike to better weight the rear tire for traction. :grin:
Thank you for participating on kdxrider.net. :bravo:
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Post by Colorado Mike »

I try to cool my bike after a tough climb by keeping air going through the radiators with as low a load on the engine as possible. Of course, this isn't always possible. Mine is a 220 which is supposed to have more problems with cooling than your 200. I ride at much higher altitude, and seldom have anything come out of the overflow tube. Unless you have radiator guards on yours, I'm kind of surprised it boiled the bottle empty. I'm wondering if the previous owner was not so careful about the water in the system, and maybe you have corrosion in the radiators. Make sure you bleed air out of the system with the valve on top of the head.

Good luck,
Mike

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Post by IdahoCharley »

Set-up is close, but assuming your still running the stock needle, the third or 4th clip position will give you more torque at low rpms. It should also allow the engine to run a little cooler and lower your need to feather the clutch.
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Post by GregS »

Lower the needle? Isn't that going to make it richer? I've gone through 2 rounds of lowering my jetting and a muffler repack to solve the huge amounts of spooge I was suffering. With the 42/152/2nd position clip settings I'm still getting some spooge, but not the gobs that I was experiencing running down the length of the muffler and all over the swingarm - including my pack-pack and jersey coated with little oil droplets.

Also, doesn't the needle impact the mid-higher revs? My guess would be that the pilot jet and air mixture screw would be responsible for the low rev fuel supply. Maybe I'm confusing low-rev with low throttle (i.e. the 1st 1/4 of throttle).

This is all great feedback! Thanks! I'm still trying to validate my first venture into the 2-smoke world -- more thread-posts/questions to come on that topic....

-Greg
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Post by IdahoCharley »

Lowering the clip on the needle will indeed raise the needle thus making the fuel mixture richer. Most notably in the 1/4-3/8 throttle area.

If the straight diameter on the needle is too small it will spooge excessively or if the pilot jet/air screw is not correct it will spooge. Most spooge problems IMO are do to low speed jetting. (If you forget about spooge while you jet - and just jet the bike so that the response is strong and smooth from 1/8 to WOT and then go back and dial in your pilot jet your spooge problems should disappear.)

The position of the clip on a given needle will NOT significantly affect throttle response above 1/2 throttle. This area is controlled by needle taper and main jet selection.

The position of the clip on a given needle WILL affect primarily 1/8 -3/8 throttle response.

Assuming your close on the main jet (which I believe you are) my approach would be to set the needle at 3rd clip position. Run the bike on a relatively flat area and listen for a fairly steady four cycling sound near 1/4 throttle which immediately clears up when a slight load is placed on the engine. Then try the same test with the clip in the 4th clip position. Then pick the better of the two clip positions. (There will be significant differences between the two clip positions. If an hesitation or stumble starts to occur about 1/4 -3/8 throttle then your too rich and want to drop raise the clip on notch on the needle)

Then reduce the pilot size and/or adjust the air screw until air screw adjustments actually affect the low speed running. Once your air screw actually makes a difference then it fine tuning from there.

NOTE - Seems to me that these 35mm carburators are fairly sensitive to initial slide height. i.e. idle screw adjustment. If you drop the height of the slide by backing off the idle screw adjustment you will increase the vacuum signal to the pilot jet. (a good thing) Once the pilot jet is more in the game it is easier to get the air screw dialed in and then finally the idle speed. Usually want to set the idle speed as slow as possible AFTER the bike has warmed up.

Good Luck - Charley
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Post by canyncarvr »

General rule of thumb is the 'B' needle slope of the OEM needle isn't the best choice. KDXers that have tried 'C' and 'D' tapers prefer them. With the OEM slide (a 5mm cut-away), a CEL/DEL would be a good place to start.

I had a pretty good boil going on in my bike just yesterday. This particular hill is known for that. My point is...it happens. I am NOT running water-wetter, Evans or anything fancy...just 50/50.

As Inda said, after such an event, after things cool down, check the rad level itself. Maybe it's OK, having sucked whatever was IN the res back INTO the rad. Maybe not, in which case anything you can put in there is probably better than nothing. At that point whether or not the water I have is 'mineralized' would be the least of my worries.

re: 'tons of stalling, high-revving, and clutch feathering' = no air thru the rads combined with very high loads on the engine.

If you expect ANY water cooled engine to take that without complaint...well, I don't think that is reasonable thinking.

I'm sure that XR got plenty hot...it just didn't have a telltale such as boiling coolant to let you know about it.

The KDX will beat the pants off it most places..acceleration, speed, throttle response, and a whole lotta more fun.

If that's not your 'schtick'..well, to each his own. Different strokes and all that stuff.

Your pilot/main selections seem pretty close. Needle tapers are responsible for the bike's 'personality'. You will be surprised at the different 'attitude' you get out of your bike with a taper change.

FWIW...anecdotal jetting info is pretty much useless, but I've run an OEM needles (-73/-74 K&L) as high as clip-5 in the summer, with perfect plug reads in every throttle position. It's easy to try...easy to change back if you don't like it.

You don't know if you've gone far enough in a jetting direction unless you've gone a tad too far!

No....a 30 second WOT scream with your new 145 main isn't a good idea! :shock:
Last edited by canyncarvr on 01:52 pm Jun 14 2005, edited 1 time in total.

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Post by skipro3 »

Overheated? Obviously. Ran out of coolant, very doubtful. Unless the radiator was damaged, it worked as it should: vent over pressured fluid from the radiator in to the overflow tank, then pull it back under vacuum when the radiator cools. How much coolant was in the radiator when you got home and checked it? YOU have checked it since riding that day right?

Don't give up on the KDX. Low RPM torque performance improvements are only a phonecall and credit card # away. Much easier and cheaper than selling the KDX and buying something else. Besides, you learned how to ride the hill on a KDX, of course the second go at it was easier. That might not be due to the XR at all. Give yourself some credit.
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Post by GregS »

Yeah, I haven't given up on the KDX yet. In fact I'll be back out this weekend.

As for my coolant, I did flush the system completely and refilled with Engine Ice.

Thanks for all the feedback and tips!

-Greg
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