KDX Overflow bottle

[colingrigson]

Does your radiator overflow bottle work for you?

Mine just seems to slowly empty out and end up empty and dry.

The hoses are good. The radiator cap seems fine. I've tried a couple of other caps, but it's still the same result. Coolant disappears from the tank, but never gets put back into it. The overflow tank looks brand new - no cracks or splits. The radiators are new aftermarket GPX. New silicone radiator hoses, no leakage into the oil. Recent top end with all new gaskets.

But I'm wondering if it's worth carrying this useless tank around. I could just run it like a later model MX bike and let the coolant expand and drain out and top it up aech time I ride.

What is your experience with this overflow bottle?

[brademan76]

my experience is very similar. when I overheat I usually only see coolant going out the rads. I should check to see if it fills the overflow next time or not...

[SpruceItUp]

How do you have the overflow for that tank routed? If it is routed down towards the ground I've noticed my coolant will disappear. I have it up around the rear fender under the seat on my 92 and it works as it should. This may not be the proper routing, but the photo in the service manual was useless, so that's what I came up with. Also, note that it doesn't need very much fluid in the tank, mine is pretty low, but there is still coolant in it (when cold) and if I put more in it I lose fluid.

I went through the same thought process you both did, but this is the conclusion I came to on my 92. I still check my fluid, but I haven't had to top off since I fixed this over a year ago. Though I have drained the coolant a couple times for repairs since.

[Chuck78]

I've been curious about this myself, more so, how the coolant gets sucked back into the engine as is described in the IMS aftermarket coolant overflow/recovery tank. I assume that if the cooling system gets pressurized when overheating, as it cools down, the radiator cap seals and stops venting into the overflow, and as the system continues to cool down, primarily with the engine off I would imagine, the pressure slowly drops in the cooling system and draws fluid back from the overflow? But that doesn't seem to be how the cap would work though to permit suction, the cap seems to just spring open and is held shut, it's not a two-way valve, so this sort of system always confuse me.

And working out the logistics of my KX 125/KDX 220 hybrid build, I considered buying one of those IMS overflow tanks, but for the cost and question on the functionality of returning coolant to the engine, I may hold off since they are over $100 and I'm not sure if the KDX overflow tank will fit as it is slightly larger, and the 94-98 KX 125/250 shrouds are quite small. I'll have to take a good look at it again and ponder while looking at the radiator cap as well.

I noticed mine always gets a little bit lower with time, but I also attributed that to me having the hose just running up into a loop and then back down, which when I frequently spill the bike over on its side and technical slow goat trail to rain, I would assume I am losing a little bit out the hose on those tip over lay downs.
Looping the hose back up and then to the rear and back down with an added length of tubing over the stock 220 and 200H seems like a better plan to prevent accidental spillage.

So the way I see it the primary function is to catch the coolant before it goes on to the ground so that you can later add it back to the system, unless somehow it does siphon itself back into the system as the engine cools. I'm not sure how that would actually work though, I'll have to investigate this further.

For technical trail riding, especially without a radiator fan, this is definitely a good thing to have.
I'll probably try and shop around and see what SPAL brand fans the aftermarket add-on kits use, and probably just buy my own unless I find a good deal on a kit. Then I might need to add a small battery to the system to assist the voltage delivered to the fan at low RPM and at idle speed for those technical trails.

[billie_morini]

My used KDX 220 did not come with a bottle. A little bit of overheating was occurring. So, I bought a new bottle and installed it. The little bit of overheating stopped. Best I can tell across 3 years, the bottle fluid level has not changed. The fluid in it still looks brand new & bottle interior remains clean

[Chuck78]

My used KDX 220 did not come with a bottle. A little bit of overheating was occurring. So, I bought a new bottle and installed it. The little bit of overheating stopped. Best I can tell across 3 years, the bottle fluid level has not changed. The fluid in it still looks brand new & bottle interior remains clean

I guess I just crash far more often than you, then, Billie! Mine disappears a bit at a time after most rides!

I'm starting to attempt to "ride my age" to a very slight degree after the badly broken wrist.
I was riding race pace, solo, on a flowy stretch in a highly technical rocky trail system 6-ish trail miles from camp where I had just turned around from the furthest point away... Split my fuel tank, I was covered in gas, fat lip,broken wrist, and I still decided to take the long way back (opted out of the route that'd hit the gravel road in order to get more trail miles!), riding WITH broken wrist masked by the adrenaline surge of the crash, slamming into a tree after getting kicked sideways by a loose rock in the trail...

I'm trying to preserve myself a bit so I can enjoy another 30 years of riding (into my late 70's!).

[SpruceItUp]

My used KDX 220 did not come with a bottle. A little bit of overheating was occurring. So, I bought a new bottle and installed it. The little bit of overheating stopped. Best I can tell across 3 years, the bottle fluid level has not changed. The fluid in it still looks brand new & bottle interior remains clean

I guess I just crash far more often than you, then, Billie! Mine disappears a bit at a time after most rides!

I'm starting to attempt to "ride my age" to a very slight degree after the badly broken wrist.
I was riding race pace, solo, on a flowy stretch in a highly technical rocky trail system 6-ish trail miles from camp where I had just turned around from the furthest point away... Split my fuel tank, I was covered in gas, fat lip,broken wrist, and I still decided to take the long way back (opted out of the route that'd hit the gravel road in order to get more trail miles!), riding WITH broken wrist masked by the adrenaline surge of the crash, slamming into a tree after getting kicked sideways by a loose rock in the trail...

I'm trying to preserve myself a bit so I can enjoy another 30 years of riding (into my late 70's!).

That sounds pretty gnarly. Glad you're doing better!

[billie_morini]

"... the long way back (opted out of the route that'd hit the gravel road in order to get more trail miles!), riding WITH broken wrist masked by the adrenaline surge of the crash, slamming into a tree after getting kicked sideways by a loose rock in the trail..."

[Chuck78]

"... the long way back (opted out of the route that'd hit the gravel road in order to get more trail miles!), riding WITH broken wrist masked by the adrenaline surge of the crash, slamming into a tree after getting kicked sideways by a loose rock in the trail..."

Yeah.. I started feeling that my wrist was perhaps mildly broken in less than a mile, when using the clutch, but the gas tank being split from the upper part of the frame all the way up to the filler neck ensured that I certainly was not riding anymore on this trip and had to sit out the next two days, so I wanted to take in those extra couple of trail miles instead of gravel road, although that was quite the reckless decision which could have ended in me walking back if I had ran out of fuel entirely, potentially requiring my bike to be retrieved with assistance. Luckily I was able to ride it back to camp, but was a bit delirious from the crash and all the gasoline fumes, with my jersey and pants soaked in fuel...

I think laying the bike down probably is the reason that the level in these overflow reservoirs depletes itself although it could potentially get sucked back into the cooling system, but I am not too sure how that would actually work. I need to look at the radiator cap functionality further on this note.

[billie_morini]

Chuck, likely you know this & it's only a reminder:

The bottle an "expansion" tank, intended to allow for coolant in the radiator/engine to expand into that tank when the engine warms up. Following engine operation, the vacuum created during cooling sucks coolant back to the engine.

[JimmyB]

I used to fill my 02 220 tank up to the full mark when I first got it but noticed it was almost empty after every ride, it never got below the low mark and concluded in rough terrain it was just spilling out the overflow tanks overflow hose, had the same experience with the 90/94 200s I had also, just keep a minimum amount in the overflow tanks. I keep it between the low mark and the lower step of the tank( about 1"/25mm) on the 220 and it seems happy there.