Runs cooler without fairing

59096 · August 1st, 2019, 05:32 AM

Is it my imagination or will the GPX250 run cooler without the fairings. I removed all the plastics on mine which has turned it into a naked bike and now it runs at 50 - 60 degrees Celsius coolant temp where as before in the same ambient temp it was running around 75 most of the time. Fact or fiction?

Triple Jim · August 1st, 2019, 05:45 AM

Seems like your measurements present facts.

59096 · August 1st, 2019, 06:54 AM

Quote:

Originally Posted by Triple Jim

Seems like your measurements present facts.

They could present facts but I am interested to see if any others have had a similar experience. 50 - 60 degrees seems somewhat low when it comes to peak engine efficiency?

Triple Jim · August 1st, 2019, 08:22 AM

Yes, it is below optimum. You can buy a Thermobob kit or make your own, and convert it to a bypass system like cars have if you're concerned about it. At that point you can put in whatever thermostat you like.

My 250 is naked, but I've never measured the coolant temperature, other than looking at the ballpark gauge reading.

Theorist · August 4th, 2019, 11:24 PM

I'd expect that naked it would run cooler in traffic or at low speeds and stops with more air cooling. With fairings the electric fan might kick on more often in heavy stop and go traffic. Running a bike really hard at high speeds I suspect that the fairings might channel more air to the radiator to more effectively prevent overheating even at extreme loads and ambient temperatures.

Your coolant temperature findings make sense but the differences might vary with the type of riding and ambient temperatures.
Posted via Mobile Device

Hexadecimus · August 29th, 2019, 01:41 PM

1. Yes, but cooler is not always better. You want to run as close as possible to the designed operating temperature. You'll get better power, mpg, less pollution, and less carbon buildup in the combustion chamber. Running too cool can do other Bad Things® too. You probably want to be about 85 to 93.333 ºC (185-200 ºF).

2. Temperature gauges are inaccurate. You'll need to remove your coolant sensor and test it with a multimeter in a pan of water with a known temperature to know the calibration, then calibrate your gauge to match using resistors. Otherwise you're just roughly in the neighborhood at best.

DannoXYZ · August 29th, 2019, 02:38 PM

Yup, datalogged information would be best. Pregens run too cold as it is, won't boil off water condensated in crankcase and lead to poor lubrication. Not to mention large delta-T beween combustion-chamber and water-jacket robs power. Honda's done some great research on ceramic engines that run much hotter than current ones, with benefits of more power and efficiency.

Some great graphs of collected data on Thermo Bob site.
Https://shop.watt-man.com/Thermo-Bob...EARS-TB3-N.htm

Hexadecimus · August 30th, 2019, 11:03 AM

Quote:

Originally Posted by DannoXYZ

Yup, datalogged information would be best. Pregens run too cold as it is, won't boil off water condensated in crankcase and lead to poor lubrication. Not to mention large delta-T beween combustion-chamber and water-jacket robs power. Honda's done some great research on ceramic engines that run much hotter than current ones, with benefits of more power and efficiency.

Some great graphs of collected data on Thermo Bob site.
Https://shop.watt-man.com/Thermo-Bob...EARS-TB3-N.htm

The diagrams there are for a KLR650 offroad bike, and I would think the temperature graphs are too. The EX250 has a 180 degree thermostat and a design that should work correctly. Funny how the guy trying to sell something portrays this... incorrectly.

Theorist · August 30th, 2019, 12:42 PM

Has anyone tried a cheaper alternative to the thermo-bob?

Since any motorcycles do have a thermostat bypass line, is it possible to use a thermostat housing for or from another bike? Would it just need to use the same size hose (5/8 inch?) and a suitable 180-195F thermostat? Some old R1 thermostats look like they could work. The cost of a used thermostat housing, thermostat, tee coupler, narrow hose, and 6 house clamps might cost around $50?

Has anyone tried just using two tee couplers? This could reduce but not stop coolant flow through the radiator and increase coolant flow through the engine when cold. Unfortunately it would also reduce coolant flow through the radiator when the engine is hot. A thermostat and housing with a built in bypass is a better solution. Could two tees might be better than stock if the bypass line is narrow enough and one doesn't run the engine very hot?

DannoXYZ · August 30th, 2019, 12:50 PM

Bypass wouldn't work without thermostat housing that does on/offswitching of bypass. The movement of thermostat opens and closes bypass. It's Y-connection that either sends coolant to radiator OR to bypass. Without opening bypass when cold and closing it when hot, you'd end up with same operating conditions as stock.

Thermo Bob is only partial upgrade to more modern cooling-system design. But final step is really not possible, to reverse coolant flow. To maintain more constant temperatures in engine, you need to send coldest coolant leaving radiator to hottest part of engine first, the head. This warmed up coolant then flows to coldest part of engine then finally back out to radiator. Toyota did this reversal back in mid-'80s.

Theorist · August 30th, 2019, 01:19 PM

Right. Two tee connections would send coolant through both the bypass and the radiator. When the thermostat is cold and nearly closed (but never fully closed with the stock design) most of the coolant would flow through the bypass. When the stock thermostat opens, most of the coolant would flow through the radiator, as long as the bypass line is narrow enough to restrict flow more than the thermostat, radiator, and pressure cap path.

The coolant will follow the path of least resistance. The resistance increases with the velocity of the coolant, so the more restricted path will carry a lower velocity of coolant than the less restricted path.

The danger, somewhat like partially blocking the radiator with cardboard, is reduced cooling capacity. The bypass line could be closed much like removing the cardboard or changing thermostats seasonally, but a thermostat housing with the bypass built in like the thermo Bob or perhaps a housing for another application would be better, because they bring bypass flow next to the thermostat. This allows use of a thermostat that fully closes.

Some more advanced automotive thermostats will close or restrict the bypass line when hot, but I don't believe the thermo Bob actually closes the bypass path. It opens the radiator path when hot, sending most but not all coolant through the less restricted radiator path.

Please correct me if I'm wrong.

DannoXYZ · August 30th, 2019, 01:32 PM

Open up a Toyota thermostat housing and you'll see how Thermo Bob is constructed. As thermostat opens, it backs up and plugs bypass hole that's situated on side of housing. Thermostat itself is part of on/off valve that determines which way coolant flows in a Y-split.

It's simply not path of least resistance because you can't do 0/100% switching with just hose sizes. Without valving switching of ports to block bypass when warm, you end up with some flow bypassing radiator when hot and compromised cooling.

But yeah, I'm not sure ThermoBob does complete blockage of bypass when up to temperature. The temp-graphs does show more optimal operations of cooling systems. Even if it's for KLR, that engine, water-pump, thermostat and radiator is configured exactly same way as Ninja 250 with complete blockage of flow until thermostat starts to creep open. Then it closes again due to getting hit with cold coolant, then opens again as coolant warms up, then closes again, etc.

DannoXYZ · August 30th, 2019, 01:52 PM

Here's picture of Toyota thermostat housing with round thermostat and radiator-hose remove from top. Coolant comes into housing at square port on right. With cold thermostat on top closed, all coolant flows out bypass round hole on bottom and is recirculated back into engine.

As recirculating coolant warms up, it opens thermostat and for while, both the bypass and thermostat has coolant flow. Then as coolant comes up to full operating-temperature, thermostat opens fully and its butt closes round bypass passage. At this point, 100% of coolant flows through thermostat and 0% goes through bypass.

Theorist · August 30th, 2019, 02:53 PM

Thank you. That makes perfect sense.

The Thermo-bob-3 for the Ninja seems it couldn't work the same way, as the bypass line is the small diameter line on the side of the thermostat. Just as the thermostat never blocks the square port on the Toyota, the thermo-bob thermostat never blocks the bypass line. At least the thermo-bob thermostat doesn't block the coolant coming from the engine at the far end of its thermostat housing.

DannoXYZ · August 30th, 2019, 06:24 PM

What can be done is drill little 4mm hole into thermostat. A lot of cars had these before converting to full bypass circuitry. Little hole typically has jiggle-valve and allows small amounts of coolant to circulate, thus not trapping all engine-side coolant when cold. This alleviates hot & cold portions of stagnant coolant in engine before thermostat opens.

August 1st, 2019, 05:32 AM	#1
59096 ninjette.org member Name: Garry Location: Bungendore Australia Join Date: Jan 2019 Motorcycle(s): GPX250 1989 model and 1990 model Posts: 98	Runs cooler without fairing Is it my imagination or will the GPX250 run cooler without the fairings. I removed all the plastics on mine which has turned it into a naked bike and now it runs at 50 - 60 degrees Celsius coolant temp where as before in the same ambient temp it was running around 75 most of the time. Fact or fiction? __________________________________________________ Perpetua Culpa Alterna Vagus

August 4th, 2019, 11:24 PM	#5
Theorist ninjette.org member Name: Eric Location: MA Join Date: May 2019 Motorcycle(s): 2005 250 Posts: 39	I'd expect that naked it would run cooler in traffic or at low speeds and stops with more air cooling. With fairings the electric fan might kick on more often in heavy stop and go traffic. Running a bike really hard at high speeds I suspect that the fairings might channel more air to the radiator to more effectively prevent overheating even at extreme loads and ambient temperatures. Your coolant temperature findings make sense but the differences might vary with the type of riding and ambient temperatures. Posted via Mobile Device
	2 out of 2 members found this post helpful.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
[nytimes.com] - From Cruiser to Cooler: Ryca CS-1	Ninjette Newsbot	Motorcycling News	0	July 21st, 2012 12:50 AM
Rear rack for cooler or Givi	Bill E Bob	2008 - 2012 Ninja 250R Farkles	8	May 14th, 2012 10:34 PM
This is cooler then a Can Am	Kevin2109	Videos	14	September 25th, 2011 10:20 PM
Even in a Honda ad, Steve McQueen is cooler than you	gfloyd2002	General Motorcycling Discussion	13	February 20th, 2011 03:52 PM
Keeping the bike cooler...	zail	2008 - 2012 Ninja 250R Tech Talk	26	July 14th, 2009 11:00 AM

August 1st, 2019, 05:45 AM	#2
Triple Jim Guy Who Enjoys Riding Name: Jim Location: North Carolina Join Date: Jul 2016 Motorcycle(s): Ninja 250 Posts: A lot. MOTM - Oct '18, Aug '17, Aug '16	Seems like your measurements present facts.

August 1st, 2019, 08:22 AM	#4
Triple Jim Guy Who Enjoys Riding Name: Jim Location: North Carolina Join Date: Jul 2016 Motorcycle(s): Ninja 250 Posts: A lot. MOTM - Oct '18, Aug '17, Aug '16	Yes, it is below optimum. You can buy a Thermobob kit or make your own, and convert it to a bypass system like cars have if you're concerned about it. At that point you can put in whatever thermostat you like. My 250 is naked, but I've never measured the coolant temperature, other than looking at the ballpark gauge reading.

August 29th, 2019, 01:41 PM	#6
Hexadecimus ninjette.org member Name: Hex Location: USA Join Date: Aug 2019 Motorcycle(s): EX250F, 1960 T100A, GPz900R, 74 XLCH, etc. Posts: 23	1. Yes, but cooler is not always better. You want to run as close as possible to the designed operating temperature. You'll get better power, mpg, less pollution, and less carbon buildup in the combustion chamber. Running too cool can do other Bad Things® too. You probably want to be about 85 to 93.333 ºC (185-200 ºF). 2. Temperature gauges are inaccurate. You'll need to remove your coolant sensor and test it with a multimeter in a pan of water with a known temperature to know the calibration, then calibrate your gauge to match using resistors. Otherwise you're just roughly in the neighborhood at best.

August 29th, 2019, 02:38 PM	#7
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	Yup, datalogged information would be best. Pregens run too cold as it is, won't boil off water condensated in crankcase and lead to poor lubrication. Not to mention large delta-T beween combustion-chamber and water-jacket robs power. Honda's done some great research on ceramic engines that run much hotter than current ones, with benefits of more power and efficiency. Some great graphs of collected data on Thermo Bob site. Https://shop.watt-man.com/Thermo-Bob...EARS-TB3-N.htm

August 30th, 2019, 12:42 PM	#9
Theorist ninjette.org member Name: Eric Location: MA Join Date: May 2019 Motorcycle(s): 2005 250 Posts: 39	Has anyone tried a cheaper alternative to the thermo-bob? Since any motorcycles do have a thermostat bypass line, is it possible to use a thermostat housing for or from another bike? Would it just need to use the same size hose (5/8 inch?) and a suitable 180-195F thermostat? Some old R1 thermostats look like they could work. The cost of a used thermostat housing, thermostat, tee coupler, narrow hose, and 6 house clamps might cost around $50? Has anyone tried just using two tee couplers? This could reduce but not stop coolant flow through the radiator and increase coolant flow through the engine when cold. Unfortunately it would also reduce coolant flow through the radiator when the engine is hot. A thermostat and housing with a built in bypass is a better solution. Could two tees might be better than stock if the bypass line is narrow enough and one doesn't run the engine very hot?

August 30th, 2019, 12:50 PM	#10
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	Bypass wouldn't work without thermostat housing that does on/offswitching of bypass. The movement of thermostat opens and closes bypass. It's Y-connection that either sends coolant to radiator OR to bypass. Without opening bypass when cold and closing it when hot, you'd end up with same operating conditions as stock. Thermo Bob is only partial upgrade to more modern cooling-system design. But final step is really not possible, to reverse coolant flow. To maintain more constant temperatures in engine, you need to send coldest coolant leaving radiator to hottest part of engine first, the head. This warmed up coolant then flows to coldest part of engine then finally back out to radiator. Toyota did this reversal back in mid-'80s.

August 30th, 2019, 01:19 PM	#11
Theorist ninjette.org member Name: Eric Location: MA Join Date: May 2019 Motorcycle(s): 2005 250 Posts: 39	Right. Two tee connections would send coolant through both the bypass and the radiator. When the thermostat is cold and nearly closed (but never fully closed with the stock design) most of the coolant would flow through the bypass. When the stock thermostat opens, most of the coolant would flow through the radiator, as long as the bypass line is narrow enough to restrict flow more than the thermostat, radiator, and pressure cap path. The coolant will follow the path of least resistance. The resistance increases with the velocity of the coolant, so the more restricted path will carry a lower velocity of coolant than the less restricted path. The danger, somewhat like partially blocking the radiator with cardboard, is reduced cooling capacity. The bypass line could be closed much like removing the cardboard or changing thermostats seasonally, but a thermostat housing with the bypass built in like the thermo Bob or perhaps a housing for another application would be better, because they bring bypass flow next to the thermostat. This allows use of a thermostat that fully closes. Some more advanced automotive thermostats will close or restrict the bypass line when hot, but I don't believe the thermo Bob actually closes the bypass path. It opens the radiator path when hot, sending most but not all coolant through the less restricted radiator path. Please correct me if I'm wrong.

August 30th, 2019, 01:32 PM	#12
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	Open up a Toyota thermostat housing and you'll see how Thermo Bob is constructed. As thermostat opens, it backs up and plugs bypass hole that's situated on side of housing. Thermostat itself is part of on/off valve that determines which way coolant flows in a Y-split. It's simply not path of least resistance because you can't do 0/100% switching with just hose sizes. Without valving switching of ports to block bypass when warm, you end up with some flow bypassing radiator when hot and compromised cooling. But yeah, I'm not sure ThermoBob does complete blockage of bypass when up to temperature. The temp-graphs does show more optimal operations of cooling systems. Even if it's for KLR, that engine, water-pump, thermostat and radiator is configured exactly same way as Ninja 250 with complete blockage of flow until thermostat starts to creep open. Then it closes again due to getting hit with cold coolant, then opens again as coolant warms up, then closes again, etc.

August 30th, 2019, 01:52 PM	#13
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	Here's picture of Toyota thermostat housing with round thermostat and radiator-hose remove from top. Coolant comes into housing at square port on right. With cold thermostat on top closed, all coolant flows out bypass round hole on bottom and is recirculated back into engine. As recirculating coolant warms up, it opens thermostat and for while, both the bypass and thermostat has coolant flow. Then as coolant comes up to full operating-temperature, thermostat opens fully and its butt closes round bypass passage. At this point, 100% of coolant flows through thermostat and 0% goes through bypass.

August 30th, 2019, 02:53 PM	#14
Theorist ninjette.org member Name: Eric Location: MA Join Date: May 2019 Motorcycle(s): 2005 250 Posts: 39	Thank you. That makes perfect sense. The Thermo-bob-3 for the Ninja seems it couldn't work the same way, as the bypass line is the small diameter line on the side of the thermostat. Just as the thermostat never blocks the square port on the Toyota, the thermo-bob thermostat never blocks the bypass line. At least the thermo-bob thermostat doesn't block the coolant coming from the engine at the far end of its thermostat housing.

August 30th, 2019, 06:24 PM	#15
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	What can be done is drill little 4mm hole into thermostat. A lot of cars had these before converting to full bypass circuitry. Little hole typically has jiggle-valve and allows small amounts of coolant to circulate, thus not trapping all engine-side coolant when cold. This alleviates hot & cold portions of stagnant coolant in engine before thermostat opens.