New rider with a 2006 250. My daily commute is about 15 miles, one way. I can take the freeway or go straight down one long street to the other side of town. When I choose the surface street, I, of course, hit plenty of stop-and-go traffic. I've noticed about half way home, say 7-8 miles down the road, at stoplights, the bike's temperature rises fairly quickly. It never actually hits red, but it's come pretty close a couple times. It immediately cools down once I get going, but it seems to me, even in stop-and-go traffic, in fairly hot weather, say between 85-95 degrees, that it should be running a little cooler. When I'm on the freeway, it's no issue at all.

The coolant is fine and the fan does come on. Is this really normal temperature, even with a liquid-cooled bike? Seems to me it should be a bit more stable on a liquid-cooled bike. Am I being paranoid or is something amiss in the cooling system?

Thanks for your time and great forum :thumbup:

I guess I'd say it doesn't sound abnormal. If the bike is fully warmed, it's warm outside, and it's sitting at a stoplight, it can certainly get on the warm side, and even close the red zone. The fan isn't strong enough to cool the radiator/engine down that much, but it's enough to keep it from getting too hot to the point of damage. Once the bike is moving again, the airflow is orders of magnitude better and the engine cools down quite quickly.

That's actually what I've been told a few times. Just curious on getting a lot of experienced opinions. Thanks for your response, Alex. :thumbup:

That's just a big difference to the way a car would run. So, for the most part, bikes just don't want to be in stop-and-go traffic much, huh?

Somewhat, but it shouldn't be generalized across all bikes. The ninjette has a quite small radiator, a smallish water pump, and not nearly as much coolant on board as larger bikes. It doesn't need much, as it's a small engine making a comparably small amount of power, which means there just isn't as much heat to remove. If Kawi had sized the cooling system large enough to keep the bike cool running while at a stop, it would have added significant weight and complexity that just isn't needed. Some larger bikes, especially more touring or sport-touring bikes (as opposed to full-on sportbikes) have plenty of excess cooling capacity and won't heat up nearly as much at slow speeds. But then there are some others, like the VFR, that get terribly hot at low speeds, with what many people believe to be an undersized and underdesigned cooling system.

Car systems aren't nearly as weight and size constrained, and they are sized to allow a car to idle indefinitely at a reasonable temperature, even if an owner doesn't check their coolant for 5+ years.

That makes a lot of sense. Never thought about it from a size perspective. Really appreciate the insight.

I've seen this on my ninjette as well. It gets up past the half way mark, then once I get moving, it goes down quite a bit. That's normal...as long as it doesn't hit the red or start spiking up and down for no apparent reason.

My gixxer runs insanely hot in traffic haha. I just sit there, watch the needle go allllllll the way up to red...then the fan kicks in...and i just watch the needle fall allllll the way back down to half. It's quite the spectacle.

http://faq.ninja250.org/wiki/Cooling_system
The fan engages at a predetermined point on the temperature gauge (they're not actually tied together in the sense of using the same temperature sensor, though). Many bikes engage the fan just below the red zone, while others have been reported engaging the fan at the mid-way point on the temperature gauge. The most important thing here is that it's entirely normal for your bike's temperature gauge to run all the way up to the bottom of the red zone before the fan comes on.

I notice the opposite most of the time: in UK weather (at the moment around 5-10 celsius) my bike temperature gauge is glued to the near bottom of the temperature gauge where the "C" range is. The bike practically never gets out of the "C" part of the temperature gauge.

Is it healthy for the bike to always run so cold? -- The fan doesn't come on though so don't think there is a fault.

On a hot day in start/stop traffic I notice what others experience here, the temperature climbs very near the red but never gets there as the fan kicks in.

My brand new '07 would get within a few mm of the line between red and black in stop & go traffic. I had checked all fluids when I took delivery. The radiator was completely full at that point. Then I had the 600 mile valve clearance check done. On the way home from the shop in 100 degree heat in slow traffic, the gauge came to rest right on the line between normal and hot, fan spinning away. The next morning, I checked the coolant level in the radiator. They hadn't filled it back up all the way. I added about 1.5 cups of coolant to fill it all the way up to the neck, and checked that the level in the overflow was fine. The bike never got that hot again.

I think it may make a big difference to this little cooling system whether it's completely full or not.

If you are really interested in what's going on in your EX-250's cooling system, if you want to know why it behaves the way it does, there's a guy named Bill Watt who has done quite a bit of thinking, researching and experimenting with Kawasaki cooling systems.

He has concentrated on Kawasaki's KLR 650, KLX 250, and Versys engines. But he's also working with EX-250s and Concours.

All of these engines share a common cooling system architecture (and a lot of the parts are identical, such as the thermostats and water pumps), so his research and experimentation with the KLR and KLX also applies to the EX-250.

So, if you're really curious about what's going on inside your Ninja's cooling system (and you have at least a 15 to 20 minute attention-span) look at this article that Bill Watt wrote: http://www.watt-man.com/uploads/TB_Testing.pdf

After working on and riding several classic 250s, I've found that each has its own individual character. My very first one only got up near the red on the hottest days, while my current one gets up near the hot range whenever I get stuck in traffic, regardless of outside temps. At the end of hte day, as long as your coolant is topped off, the fan comes on, and it never gets into the red then you're normal.

If you are really interested in what's going on in your EX-250's cooling system, if you want to know why it behaves the way it does, there's a guy named Bill Watt who has done quite a bit of thinking, researching and experimenting with Kawasaki cooling systems.

He has concentrated on Kawasaki's KLR 650, KLX 250, and Versys engines. But he's also working with EX-250s and Concours.

All of these engines share a common cooling system architecture (and a lot of the parts are identical, such as the thermostats and water pumps), so his research and experimentation with the KLR and KLX also applies to the EX-250.

So, if you're really curious about what's going on inside your Ninja's cooling system (and you have at least a 15 to 20 minute attention-span) look at this article that Bill Watt wrote: http://www.watt-man.com/uploads/TB_Testing.pdf

Speaking of Bill Watt, Exploring/Carolina has installed a Thermo-Bob system designed by Bill Watt on his bike. Check out his thread. http://www.ninjette.org/forums/showthread.php?t=88799&highlight=thermo+bob

Yeah just wait till you get a 600, or 1000. These damn things run hot in traffic, to the point of if I touch the frame it hurts lol talk about a heater

Speaking of Bill Watt, Exploring/Carolina has installed a Thermo-Bob system designed by Bill Watt on his bike. Check out his thread. http://www.ninjette.org/forums/showthread.php?t=88799&highlight=thermo+bob

I also installed a Thermo-Bob. I love what it does for my EX-250.

I agree 100% with Alex's comments, and unlike the original poster, (lives in 'hot hot heat' !), I live in the UK, which can never be described as 'hot hot heat',
I find that even in averagely cool days, if I stop and let the bike idle after reaching temperature, the temp gauge after just a minute will rise quickly and the fan kicks in. Doesn't seem a problem, though I would never leave it idling for long other than when tuning up. Oh, mine's an '89 pre-gen.

I replaced my coolant with Mercury. Seems to make it a lot more stable. I just wish it didn't leak so much! Topping up the mercury every week is expensive.
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I replaced my coolant with Mercury. Seems to make it a lot more stable. I just wish it didn't leak so much! Topping up the mercury every week is expensive.
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It's a little early in the day to be drunk.

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