Relatively easy to overheat?

[Chopperpilot]

So I'm new to KDXs and new to off road riding in general. My other bike is a KLX650R (1996 model with the radiator fan). Does anyone else think the H series (mine is a 2001 200) is a little easy to overheat? I live in Alaska, so I'm riding in temps from 45-85. Lately I've been in the 50's. Now 'normal' trail riding I never have an issue. When I'm 'training' and practicing hill climbs, clutch bite point, or clutch ups, I find it's going to cause a boil over after about 15-20 minutes. Now obviously I know that this particular type of training is exactly the thing that's going to cause an overheat (slow speeds, lots of clutch slipping, etc). I'm just a little surprised that in these temps it happens pretty quickly in my opinion. The KLX650 takes a bit to get the fan to come on when practicing hill climbs, but it will come on and not boil over (earlier 650R models without the fan were noted for overheating in slow stuff). It's possible that I just need to replace the radiator cap with a new one that will hold the correct pressure I guess? I haven't checked that yet. Anyone else have any opinions on what to look for? The bike runs great, radiators look great inside and out.

[Chuck78]

Are you running the OEM plastic radiator louvers? If they're missing, especially if running Devol radiator guards, the KDX will be a bit more prone to running hot. I ride slow technical tracks often, but I'm not sitting still doing clutch exercises for 15+ minutes. Steep hill climbs? If you're doing a big steep technical hill climb, and turning around and coasting down with clutch disengaged (water pump moving only at idle speed), then sitting stationary for a few moments prior to repeating again, then yes, the engine could get a bit hot.

I've only boiled over my KDX's once, when getting really stuck in some quicksand strip-mining byproduct nasty mud at our preferred local-ish technical trails @ Perry State Forest APV Riding Area. That was 88 degrees with high humidity, spinning the tire @ 7000rpm+ on the engine repeatedly, with zero ground speed, for maybe a couple long spurts over the course of 1-2 minutes total, while in the middle of a slow 2nd gear trail run....

Keep in mind, modern 450's & KTM 500 EXC-F's are notorious for overheating in slow singletracks... Even 10-15mph somewhat flowing slow tracks AND with cooling fans, the 500 EXC-F boils over once it slows to 10-15mph in hot humid summer heat.
Also, 300 2-strokes are seen semi-regularly boiling over in prolonged technical rock sections etc (Tennessee KnockOut hard enduro race) even WITH cooling fans...



I'd first pull your radiator cap when the bike is warming up and see if you have a large amount of bubbles flowing in your coolant to the top of the radiator. Thtos could mean a compromised head gasket or head gasket sealing surface (slightly warped head).

After that, I'd say perhaps 20 minutes of almost no significant airflow may be a bit much if you have no air bubbles in the coolant.

[Kawibunga]

Funny enough, we were out with the 220s this weekend. Nasty steep single track in the mountainous foothills out this way. My stock 02 was fine. My 18 years olds piped 02 was fine. My 20 year olds stock 01 boiled over at the the top. Keep i mind it was several tries to work ones way through the trees with starting and stopping etc to try to make it........... so I guess they can boil over (first time it's happened). And Chopperpilot, I actually tried most of this same trail on the 650R earlier in the year with no over heating. But there is not way I would have made it to the top with it. I'm not a good enough rider and the slow speeds and weight would have gassed me I'm sure!

But good point Chuck78 about the Devol Rad gaurds. I have set with new rads (yet to install them, next season) so I'll keep that in mind. May look into potentially running fans too.......

[Chuck78]

Here's a photo I saved (I believe from a KDXRider member) of what really should be done to the Devol radiator guards if using them with no plastic louvers. I'll try and check this week to see if the OEM louvers fit still, with the Devol guards, but I believe the answer to that is no.

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It really helps direct the airflow (which is partially blpcked by the forks) into the radiators to have these in place. The Devol guards are a lifesaver at times, but also a hindrance to low speed cooling.

This winter, I should either learn to TIG weld, or use my MIG's spool guns with aluminum wire, to add these aluminum louvers to my both pairs of my Devol guards, or else modify them to accept some plastic OEM guards.

Purple anodized Devol guards would be really awesome
Perhaps I need to buy a DIY anodizing kit as well

[Chopperpilot]

On my practice hill I found (unexpectedly) that the KLX650R was much less of an emotional event to get to the top the first time I tried it. I was skeptical about dropping the big bike on it, but with that tractor motor + 4 stroke traction...... it just went up it.
I'll say that when my KDX boils over, it doesn't 'seem' particularly hot, so I am wondering if its just an issue of the radiator cap not having the correct spring pressure causing it to boil over a little too quick (IMO) on things that will obviously tax the coolant system. Because as stated, I've boiled mine over several times it what you lower 48ers would call 'cool' weather. Now I can trail ride all day with no issues including hill climbs, but if I abort a hill climb and end up having to take a few swings at it, or doing my 'practice' it's a for sure thing. The cap spring pressure is an important part of keeping the coolant from boiling.

[billie_morini]

I ride steep technical mountain tracks in Central California. It's tough on the machine (because I can only go slow!). My DRZ 400S has a fan that sometimes runs. My KDX 220 was designed & manufactured without a fan. It gets pretty hot sometimes. I've seen a little bit of hot water / steam a few times. It happened more early on because the previous owner removed the coolant system expansion tank. I bought a replacement OEM tank & installed it. This helped a little bit.

At least one rider (racer, actually) installed a fan (Moonstomper, I think) on a KDX. Of course, to do this requires adequate battery and on-board charging system. Not that difficult to do.

Anyway, I use radiator caps in my DRZ and KDX that incorporate a temperature gauge (photo below and link https://www.amazon.com/gp/buyagain/sear ... _bap_m_srh).

My KDX also has a Vapor Trail Tech with a temperature gauge fed by thermocouple. The thermocouple came with the Trail Tech and is installed in the coolant piping at the location that coolant exits the engine. Here's the forum link for this: viewtopic.php?f=86&t=25268&hilit=thermocouple

[SS109]

Hmm, never had a problem with my modded 220 overheating even riding hike=a-bike stuff.

First thing I would do is make sure you have fresh coolant (should be changed every year anyway) and run a higher pressure radiator cap. If that isn't enough, make sure the bike isn't running too lean, that you are running 91 octane (yes, running 87 I've noticed my KDX's run/ran hotter), and lastly, maybe add a fan using a temp switch and a small battery pack mounted behind the headlight.

[Chuck78]

I ride steep technical mountain tracks in Central California. It's tough on the machine (because I can only go slow!).
My KDX 220 was designed & manufactured without a fan. It gets pretty hot sometimes. I've seen a little bit of hot water / steam a few times. It happened more early on because the previous owner removed the coolant system expansion tank. I bought a replacement OEM tank & installed it. This helped a little bit.

At least one rider (racer, actually) installed a fan (Moonstomper, I think) on a KDX. Of course, to do this requires adequate battery and on-board charging system. Not that difficult to do.

Anyway, I use radiator caps that incorporate a temperature gauge (photo below and link.

My KDX also has a Vapor Trail Tech with a temperature gauge fed by thermocouple. The thermocouple came with the Trail Tech and is installed in the coolant piping at the location that coolant exits the engine. Here's the forum link for this: viewtopic.php?f=86&t=25268&hilit=thermocouple

I, too, am running a thermometer type 1.8 Bar radiator cap, and have been since overheating the one and only time (badly stuck in quicksand type strip-mine soda ash clay mud runoff) 1.5 or 2.5 years ago. It's nice to have so I know when I need to get the bike moving faster ASAP or take a break if it's all slow going ahead.
Engine Ice coolant definitely helped reduce engine temps, but as a side effect, the bike has trouble maintaining over 130-150°F in cold weather riding, where it didn't previously with Maxima Coolanol... In hot weather it's maybe 5 degrees cooler.
I try to keep it between 145-205°F. What temps do you see in the hot summer, Billie? I'll see 150/165 on 3rd 4th gear trails riding casually, but with aggressive fast riding and mixed in technical climbs and obstacles, it'll be 190-205° F


This is where I like to ride semi-locally (54 minutes from home), Perry State Forest, the bikes do run a bit hot,and this isn't even in the mountains with high altitudes and loooonngg steep grades! Singletrack heaven for Appalachian Southeastern/Eastern Ohio at least! This is the one place I've boiled over my KDX220...

[Chopperpilot]

No issues with those amazon caps? I was looking at them but the reviews on the ones I saw didn't give me a warm fuzzie

[billie_morini]

Chopperpilot: the Amazon screenshot & link provided by me (above) is the very radiator cap I'm using on my DRZ & KDX.

Chuck78: Oh my, you are a handsome bearded young man! That terrain looks rough. I'll remember and provide the answer to your question about the temps I see on my KDX in hot ambient conditions. I'll share the answer and a few photos like you did once I remember.

[Chuck78]

I think the Amazon caps are the exact same as the Tusk versions which also look exactly the same as the Mylers Radiators version.

Those pictures were taken BY me, of my KDX220, & 1 of my buddy Paul on a '99 KDX200 at that same spot, but I'll pass along the compliment!
Notice the 2 KDX's but only 1 rider in this shot from the opposite side of the other?

Screenshot_20240917-235208~2.png (3.51 MiB) Viewed 3172 times

This Redbird Crest Kentucky campsite rest stop picture was taken BY me and OF myself + my KDX220 & my lovely lady & her 3" lowered '07 KTM 200 XC-W



Bearded fella, yes. Young? The unavoidable prospect of turning 50 in 3.5 years is a bit disturbing to me
Like my 75 yr old Dad says, "Well... It's better than the alternative!"

[KDXGarage]

lots of purple, young man

[Kawibunga]

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PXL_20240914_164606039.jpg (211.77 KiB) Viewed 3138 times

Beard... yes. Purple bikes...... no ......... but my 76 year old Dad did say the exact same thing! And I'm 50 and there were guys out there way older than me, so a guy has lots of years of ripping left hopefully! A 2001 220 (20 year olds) and 2 2002s (mine & 18 year olds)

The dot on the Map is where we stopped for the pic and a rest. Where the blue line ends is where we boiled over the 2001. About 5900 ft elevation (topo lines are listed in meters on the screen capture) Cooler weather and elevation and humidity did have the 2001 stalling though, may be jetted a bit rich........... may try some waterwetter in it, ran that in my old CR500

[Kawibunga]

Beauty area to ride though.......... a couple weeks before that on my 650R

[kdxdazz]

My fan set up

[Kawibunga]

That's a neat setup kdxdazz - I'm already running a big lithium battery pack in the "tool bag" that I have wired up to a USB cable to make sure i don't run out of power for GAIA GPS on my phone. I might have to look into something like that this winter. It would have lots of power to do it......

[Chuck78]

My fan set up

How waterproof are those fans?
I suppose you could run them off the bike's aftermarket 12v rectified DC system and a small battery as well, right?

[billie_morini]

Temperatures I usually see on the little dial gauge radiator cap: I see a lot of 150F. When really hot I see 175F.

[billie_morini]

Wow, there are some really great photos showing up in this thread! Like the fan and battery pack that kdxdazz showed.

[kdxdazz]

My fan set up

How waterproof are those fans?
I suppose you could run them off the bike's aftermarket 12v rectified DC system and a small battery as well, right?

The fans are noctua industrial ppc computers fans, basically the best computer fan money can buy, I forget the IP rating , they are shower proof but not waterproof from memory but the 24 volt versions run underwater
There's probably lots of ways they could be run but given I am electrically incompetent this is the system I came up with
They flow 200cfm but it's over the whole radiator surface, you basically can't run an off road bike in the Thai jungles here without a fan
They only come in 120mm and that size is very difficult to fit on a kdx, 100mm would be ideal