Is the fan supposed to stay in all the time?

[Omarel]

I turned on my bike in neutral and noticed the fan wasn't running. Is it ok or is the fan supposed to run all the time.

[RacinNinja]

Fan comes on at XXX degrees and turns off when it reaches XXX degrees. In other words, no, it only comes on sometimes. It's controlled by a thermo switch.

[jkv45]

In normal riding (read - moving) the fan won't run at all most of the time. The exception would be moving slowly in heavy traffic in hot weather.

The fan's job is to pull air through the radiator when there is little or no forward motion and the water temp has reached a point that cooling is required.

[Bob2010]

I wish we had a temp readout and or a fan override

[Triple Jim]

You mean one of the design improvements of the Newgen was eliminating the temperature gauge? That's a bummer.

Rigging up a fan override switch would be simple enough, but I'm not sure why I'd want one, since it's automatic now.

[Flying]

The ninjette engine is known to be colder than desired, rather than warm. Look up discussions of the Thermobob

[Bob2010]

That's interesting. Reason I suggested that was because the 09 fan seems to run 2x as much as my '10

[Omarel]

Cool. Thanks guys.

[FrugalNinja250]

The fan/radiator can't pull the temperature down below the thermostat temperature rating. The fan switch off temperature is above the thermostat fully open temperature.

[Ghostt]

If you want to add a switch, you'll need a SPDT

Another common switch-type is the SPDT. SPDTs have three terminals: one common pin and two pins which vie for connection to the common. SPDTs are great for selecting between two power sources, swapping inputs, or whatever it is you do with two circuits trying to go one place. Most simple slide switches are of the SPDT variety. SPDT switches should usually have three terminals. (Sidenote: in a pinch an SPDT can actually be made into an SPST by just leaving one of the switch throws unconnected).


So you can hook the radiator switch to one side, and on the other hook either a ground, or positive depending on which one the radiator switch does, I know on PreGen it supplies the ground, don't know about NewGen.

Personal I added several small holes to the thermostat itself, this allows some water to flow while it's closed.

[Triple Jim]

Originally Posted by Ghostt

Personal I added several small holes to the thermostat itself, this allows some water to flow while it's closed.

Doesn't the stock one have a built-in leak? I haven't had mine out to see it yet, but others I'm familiar with do.

[Ghostt]

Most thermostats have a small hole, aka steam hole it's called sometimes.

I added several small holes to the outer edge of mine, thus allows some water to flow while it's closed.

[Triple Jim]

Do you find that it warms up slower in cold weather, or are the holes so small as to not make much difference that way?

What was your reasoning in adding the holes?

[Ghostt]

Originally Posted by Triple Jim

Do you find that it warms up slower in cold weather, or are the holes so small as to not make much difference that way?

What was your reasoning in adding the holes?

The holes are small, 3/64" ? haven't noticed any bad effects, it does seem to warm up quicker, and keep the temperature more constant. On my PreGen the temperature gauge sits just above the second line, almost all the time, regardless of ambient temperature.

The reason for added the extra holes was to allow a little more water to flow while the thermostat is closed, part open, etc.... Kinda like a very poor man thermobob.

I've used the trick before many many times, for many years, since my drag racing days.

[Triple Jim]

I looked around in the manual and on the web, and it appears that the 250 doesn't come with a bypass feature. It looks like when the thermostat is closed, only the coolant that gets through the small "steam hole" circulates. This is different from automotive systems I'm used to that circulate a lot of coolant through the pump, bypass hose, and engine while the thermostat is closed, with the thermostat keeping coolant from circulating through the radiator until it opens.

This also seems to be why the Thermobob system was developed... to add the bypass hose to make the system work like most cars do.

Am I reading things correctly?

[Ghostt]

Originally Posted by Triple Jim

I looked around in the manual and on the web, and it appears that the 250 doesn't come with a bypass feature. It looks like when the thermostat is closed, only the coolant that gets through the small "steam hole" circulates. This is different from automotive systems I'm used to that circulate a lot of coolant through the pump, bypass hose, and engine while the thermostat is closed, with the thermostat keeping coolant from circulating through the radiator until it opens.

This also seems to be why the Thermobob system was developed... to add the bypass hose to make the system work like most cars do.

Am I reading things correctly?

Hence why I added the additional holes.

[InvisiBill]

Originally Posted by Triple Jim

I looked around in the manual and on the web, and it appears that the 250 doesn't come with a bypass feature. It looks like when the thermostat is closed, only the coolant that gets through the small "steam hole" circulates. This is different from automotive systems I'm used to that circulate a lot of coolant through the pump, bypass hose, and engine while the thermostat is closed, with the thermostat keeping coolant from circulating through the radiator until it opens.

This also seems to be why the Thermobob system was developed... to add the bypass hose to make the system work like most cars do.

Am I reading things correctly?

Exactly. This seems to be a pretty common setup on a lot of Kawasakis (and probably other budget bikes, but I have no firsthand experience). The lack of flow means the thermostat doesn't get warmed up and stays closed, which means a lack of flow, which means the thermostat stays closed, which means a lack of flow...

Adding a Thermo-Bob bypass allows the coolant to circulate through the engine constantly, and the thermostat opens the loop up to the radiator when it gets up to temperature. Rather than just turning the flow on and off with the temperature, it's always flowing in a loop, and going through the radiator when it needs to cool down. This lets the engine get up to temp more easily, and I'd assume that the water pump is happier pushing the coolant in a loop rather than against the closed thermostat.

[Triple Jim]

Thanks Ghostt and Bill. Actually, a centrifugal pump like the water pump is easier to turn when the flow is blocked, because the liquid just swirls around in a circle, so less HP is used from the engine when the thermostat closes and nearly stops the flow. It's like when you cover the hose of a vacuum cleaner and the motor speeds up. But that's not much of a reason to skimp on the system.

[FrugalNinja250]

Thermostats typically have a small amount of leakage, this allows heated coolant to reach the thermostat so that it can react to temperature changes as the engine warms up. This leakage can be in the form of a hole (or holes), or notches, or other design features. Vehicles have heater cores, and since you want all the heat you can get as early as you can get when commanding the HVAC systems to heat vehicles typically have a separate coolant loop that bypasses the thermostat. The loop is normally parallel to the radiator, and often there is a restriction in the loop juncture to ensure enough flow differential to keep the heater core hot. Bikes don't have separate heater cores, just the radiator.

I've looked at the Thermobob and honestly don't think it does anything useful. As has been stated, water pumps typically have lower turning resistance when stalled such as when the thermostat is fully closed. You want the least amount of flow through the system while warming up so that you can decrease the time until the system is at operating temperature. This is more important on fuel-injected systems because mixture is richened when cold, and excessive time running rich can damage cylinder walls, carbon the valves and pistons, and contaminate the oil faster.

[Triple Jim]

An advantage to having the bypass system is the elimination of hot spots during warmup. But obviously an aluminum casting also tends to warm up uniformly from its own high thermal conductivity.

Overall, I tend to agree with you, FrugalNinja250... there probalby isn't enough reason to modify the cooling system of one of our 250s to make it worth the trouble, if there is any benefit at all.

[InvisiBill]

The single loop leads to surges in temperature though. Without flow (my 500's thermostat has a ~1mm bleed hole), the coolant in the engine will get much warmer than the thermostat's temperature (since the thermostat is still sitting in the cold coolant). When enough heated coolant makes it to the thermostat to open, then the cold coolant from the radiator rushes into the engine. On the KLR which has the thermostat mounted right at the engine, this was sometimes cold enough to close the thermostat again, meaning another batch of cold coolant sitting in the engine until it got warmed up again. The stock setup had at least 35°F difference between the top and bottom of the cylinder during his 20 minute test ride, as much as 115°F difference when the thermostat first opened.

With the Thermo-Bob, you're heating a slightly larger amount of coolant (the engine's capacity, plus the loop to the thermostat and back), but it's flowing constantly so it all stays at basically the same temperature. You can choose a thermostat temp that matches what you want the engine to run at, instead of having to compensate for the lack of flow. When the loop gets too hot, the thermostat opens and the radiator cools it down. If it gets cool again, the stat closes and it goes back to just the bypass loop. With a Thermo-Bob, his KLR had about 20°F difference in the worst-case scenario, usually under 15°F.

Here are the graphs from his testing:





It gets up to proper temp quicker, and fluctuates a lot less, from a cold start. It's probably much less of an issue in Texas, but I've ridden in 20°F weather when there wasn't snow. The warmer your climate is, the less you need a Thermo-Bob, but his testing showed better results even in 70°F weather. When you don't have to compensate for the lack of flow from the engine to the stat, you can choose a stat temp that better matches desired engine temps. This allows it to get up to temp when the weather is cold, without impacting cooling when it's hot. With a bypass, you could even throw a huge radiator on to increase cooling capacity, without any negative effects when it's cooler (since the coolant completely bypasses the radiator unless it's hotter than the thermostat temp).

I think the "Averages" graph does the best job of showing the overall difference between stock and Thermo-Bob. With the TB, it's 185°F ±7 for the entire ride, and gets there within 3 minutes of starting. Stock, it takes 13 minutes to get up to 140°F and peaks at 145°F after 16 minutes, half of that on the highway. However, the graph completely hides the massive in/out differences (35-115°F) shown by the delta graph. I'm no expert, but I don't think throwing 50°F water on a 165°F engine is the best idea. 500s are somewhat known for ovaling the cylinders, and I doubt these temperature variations are any help in that regard.