Overheating with Flatland radiator guard

My coolant temperature warning light came on today when I was riding at highway speed. Ambient temperature was around 90°. This is the second time I've had the warning light come on since installing the radiator guard last month. This concerns me since it's going to get WAY hotter than 90° here very soon. I bought the bike last July and rode it here through the end of last summer with no problems. I did reinstall the lower half of the fan shroud when I installed the radiator guard. My next step will be to try it without the fan shroud; just wanted to hear if anyone else has had this happen after installing a radiator guard.

I'd check coolant level then check operation of the fan then I'd look into changing coolant with engine ice.

I am not sure the fan shroud would make a difference .. I thought the only good it did was to stop hot air from blowing on your leg. Worth a try though.

I wouldn't expect the fan to come on, or make a difference if you're over-heating while running at highway speeds.

90 degrees is pretty warm, but not excessive.

This situation has only occurred since you've installed the rad. guard?

Do you know exactly what coolant you're running and what ratio the mix is with water?

I've run my X pretty darn hard for a few hours straight in 90+ degree summer weather and never had the temp light come on.

I'd check and/or replace the coolant for starters.

Again, if the light is coming on while you've got 50 mph or more winds coming directly into radiator, I doubt the fan or fan shroud will have much effect. Might be worth a try, but seems like a long shot.

Not sure who makes a more open radiator guard, but that may be your best option if your coolant is not the issue.

I would definitely be checking the fan operation first.

We learned when Zed smashed his radiator (no leaking) & fan (jammed so it wouldn't run) with his knee last August that the fan on these little bikes DOES come on a lot, at road speeds. He kept having the light come on and needed to play with speeds to lower the load on the engine until we could get it back to the Sprinter where there were enough tools to deal with the issue.

Thanks y'all for your thoughts. Coolant level is OK, and the fan is working. I just have 4000 miles on the bike, so it still has the original coolant. Is the coolant added during dealer prep? I guess it's possible that they put in the wrong mix of antifreeze & water.

motokid, do you have a radiator guard on yours?

I'm thinking that the problem may be from the absence of the OEM plastic louvers that direct airflow in to the radiator, plus the fact that the radiator guard is now somewhat restricting airflow. ??
I may try opening up the front of the guard a little if the problem persists.

Nah...no guard on mine.

Guess I need to pay attention to my fan a bit more. I never notice it running most of the time.

I think stores like Pep Boys sell coolant checkers that will tell you how much protection you have by just sucking some liquid up into the device. Might be worth a purchase.

I have a tester like the one pictured, and I was using it probably at the same time you were posting! It indicated freeze protection to -35° F, so that tells me that the antifreeze/water ratio is correct.

Subscribed. I've got the Flatlander Guard so I'd like to hear the outcome.

Check the thermostat? They go off frequently.

I think the fan is a code 51. Took me forever to press all the buttons then remember the last step of hitting the kill switch to activate the code selection when I checked mine.

i just received my Flatland Radiator Guard, and was thinking of installing it today for a dual sport ride with my group tomorrow.

after reading this, i may hold off so that i can test it first.

keep us posted with your outcome on your situation.

my bike is still under 200 miles. after my ride tomorrow i will install the guard and test it on the open highway. maybe not Sunday, but soon.

motokid wrote:

I wouldn't expect the fan to come on, or make a difference if you're over-heating while running at highway speeds.

90 degrees is pretty warm, but not excessive.

This situation has only occurred since you've installed the rad. guard?

Do you know exactly what coolant you're running and what ratio the mix is with water?

I've run my X pretty darn hard for a few hours straight in 90+ degree summer weather and never had the temp light come on.

I'd check and/or replace the coolant for starters.

Again, if the light is coming on while you've got 50 mph or more winds coming directly into radiator, I doubt the fan or fan shroud will have much effect. Might be worth a try, but seems like a long shot.

Not sure who makes a more open radiator guard, but that may be your best option if your coolant is not the issue.

Motokid is right about the airflow. Like a car, at highway speed, the fan won't run because the air pushing through at 50+ mph provides the necessary airflow. The guard does reduce the surface area that air can pass through & will not allow the radiator to dissipate heat as efficiently as the stock deflector. Adding to the heat issue is the fact that at highway RPM, the engine works harder to maintain speed & thus puts out more heat & these two issues combined causes the coolant temp to get a little hotter than before. The guard probably works fine when you're off-road low speed running because you are not taxing the cooling system by running at high speed pushing through the wind. I'd verify the coolant temp with an infrared thermometer to rule out the t-stat & maybe switch back to the stock deflector to see if it goes back to normal. More than likely, it's an airflow restriction problem.

[quote="sswrx"]

motokid wrote:

Motokid is right about the airflow. Like a car, at highway speed, the fan won't run because the air pushing through at 50+ mph provides the necessary airflow.

This is simply not true. Bikes and cars *may* have the fan run at any ground speed, depending on the heat being given off by the engine at the time.

The only time either of our bikes has had the temperature light come on was when ZED's fan was non-operational. The bike overheated at a wide variety of speeds, from slow off-road to full speed on-road. It is all about how much power you're asking the bike to deliver. He was able to limp the bike back to where we'd parked the Sprinter without engine damage by carefully keeping the engine in an RPM range that didn't ask it for too much power.

I'm running a Flatland and have had no over heating issues. And have run the bike in Moab with no issues.

Two WR's, both with rad guards and all the stock plastic under the panels removed, and I've never seen the temp light except when the coolant level was low and I've ridden this bike in just about every kind of weather and temperature and trail condition you can think of. Thermostats and fans can both easily fail, if your coolant level is good I'd look there next. I run the standard 50/50 mix with an appropriate amount of redline water wetter.

i went on a 200+ mile ride on Saturday with my new Flatland radiator guard and had zero issues. mostly highway at speeds greater than 60mph.

No issues with my rad guard.

No issues here yet either. Ambient temperature on my Saturday ride was pushing 80 on dusty trails. At times I could have walked faster than we were moving.

YamahaTN wrote:

No issues here yet either. Ambient temperature on my Saturday ride was pushing 80 on dusty trails. At times I could have walked faster than we were moving.

same here. spent the weekend in moab, temps in the 80s & a lot of low gear moving. fan kicked on a lot but no overheating.

Update: I realized that the only time mine overheated was when I was riding at warp speed on the highway from town up to my turnoff, and when temps were in the high 90s or greater. There is a very slight grade (400 ft. rise in elevation in 6 miles). I guess it was just asking too much from the little 250 to pull that grade at WOT. It's not me, I tip the scales at 160 lbs. in full gear. So now I take it a little easier when it's that hot and it hasn't overheated since. I also opened up the radiator guard a little to improve airflow. I don't have any scientific data to prove it, but I feel that it's got to help.
Y'all think 80s is hot? It has hit 108° here already, and that was back in April!

Another update:
Since my last post the bike overheated once again, when climbing a big hill at highway speed with an ambient temp of 105°. I had forgotten about the shroud at the back of the radiator, so I removed it the other day. Today I rode up the grade to my house at the speed limit (70mph) without incident. When I got home the temperature at my house (where it's higher elevation and thus cooler than in town) was 103.5°. Looks like the overheating problem is solved; now I just have to figure out what to do about my right leg being broiled! Typical aftermarket part--solve one problem; cause another!

OK, I removed the shroud at the rear of the radiator and no more overheating. But my right leg has been getting cooked from the heat. When the temperature is already 105° that hot air from the radiator is just too much. I came up with this super deluxe mod which solved the problem, and didn't cost me a dime. I cut a piece of plastic from an antifreeze jug and slipped it in behind the side panel. I dirlled a hole in the side of the radiator guard and secured the plastic with a machine screw & nut. It works!

I first saw my bike overheat after dropping it on its side and smashing the fan (aprox 6k miles). After replaceing the fan it never overheated. I then installed the Flatland guard last winter(aprox 14k miles). No problems all summer. A few weeks ago (aprox 18k miles) I replaced the two small hoses, because the bottom one split on me and replaced the old coolant with new coolant. The Yamaha/Honda dealer said the Honda coolant was the same as the Yamaha stuff. Last week I experienced the overheat on the highway that is being reported on this thread. I checked the coolant level in the overflow and made sure the radiator was full. I guess its time to check the coolant mix.

Any other suggestions?

Did you remove the shroud at the back of the radiator? That seemed to make a big difference on mine. Since my last post I also added a homemade scoop attached to the front of the radiator guard to direct more air into the radiator. It has been cooler here lately (90s instead of 105+), so it hasn't been a true test of this mod. I can however feel more air on my leg, so I think it is working. I'll find out next summer.

I haven't, but I'll give it a try. Nice Mod! If I still have problems I will try your mods. I have a 90+ degree ride home today, we'll see what happens. Its just weird that I have had no issues all summer until I replaced the hoses and coolant. The coolant I used was a Honda product, 50/50 no mixing required.

I have a 2009 WR250R with 2000 miles and it bone stock except for lower gearing and the throttle adjustment. It overheats on the freeway at WOT and 100F ambient. Fluid is good and fan works. If I keep it under 65, all is well.
The heat off the radiator already cooks my leg so I did not want to take the rear shroud off. However, that homemade jug deflector 800 made may be the trick.
Glad to know I am not the only one with this issue. Though, this issue does make me miss the twin radiators on my KLR250.
Thanks for the ideas.
IdahoWR