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Discussion Starter · #1 ·
Can someone who knows the cooling system elaborate on all its parts and workings?
 

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Theres a radiator, water pump, thermo fan and hoses. The water enters in one point runs around the cylinder block/head to keep the temperatures cooler than what air can then exits and runs through the core again.
While the bike is rolling the radiator relies on the air thats running through the core to cool off the excess heat thats being created by the hot water. If theres no air or too low a volume the temp sensor recognises that it has to kick the fan in to replace the air over the core.
The engine isnt as hot as what your what you think and temp gauge is a bit of liar at times depending on air temps etc. Probably the easiest fix for the bike is to use 2 fans instead of one in hot enviromemts......still havent seen anyone do that but.

Did that answer your question?
 

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Discussion Starter · #3 ·
Just what I wanted! Is the water pump on all on the time or controlled by the thermostat/ECU?
 

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The pump is on all the time.
The radiator fan is controlled by a thermoswitch. Coolant flow is controlled by a thermostat.
 

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The pump is on all the time.
The radiator fan is controlled by a thermoswitch. Coolant flow is controlled by a thermostat.
The thermostat gets no mention in the workshop manual but I suppose this is because it sits so obviously as a T junction in the pipework. Easy to check that its working by feeling the temperature in each pipe.
 

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Discussion Starter · #6 ·
Coolant flow is controlled by a thermostat.
If the pump is on all the time, isn't the coolant 'flowing' all the time? How does the thermostat control and drive this?
 

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Discussion Starter · #8 ·
Yeah, coolant is flowing all the time but: Either the coolant goes through the radiator or the radiator is bypassed.
I don't get it, what's it 'flowing through' if not the radiator?
 

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The water that remains inside the cylinder and head. Once it gets too hot the thermostat opens and pushes new water in while extracting the hot water.

Wheres the thread that has the 390 break down, its all explained in there. I was just going through it on my ipad, its on my dropbox but I dont have the app on here.
 

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Discussion Starter · #11 ·
Nice, that sums it up. Thank you all!
 

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Posting here rather than start a new post as it is related.
Has anyone here on the forum (in the hotter countries) ever ditched the thermostat in order to improve the coolant flow and improve the cooling?
Temperatures here (Southern Laos) hardly ever get below 20C and I think (taking it easy the first few km's) we do not need the thermostat.
Anyone that has tried this, I'd be very happy with your experience and possible T piece you have used.
Trying to keep cool ;)
 

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Posting here rather than start a new post as it is related.
Has anyone here on the forum (in the hotter countries) ever ditched the thermostat in order to improve the coolant flow and improve the cooling?
Temperatures here (Southern Laos) hardly ever get below 20C and I think (taking it easy the first few km's) we do not need the thermostat.
Anyone that has tried this, I'd be very happy with your experience and possible T piece you have used.
Trying to keep cool ;)
I don't think it will help. The thermostat is fully open at 96C, while the fan switches on at 96C and off at 90C. Those are actually pretty low temps by motorcycle standards (at least by the ones I have owned) and I suspect that the fan cycling on and off so frequently may be the reason many owners think their bike is running overly hot. The temp gauge also seems to encourage riders to think they are overheating too easily -- if the gauge had actual numbers instead of just bars I think we would see that the condition is not that bad. I know that when my fan comes on it drops the temp fairly quickly, and if it can get it down to 90C that's cool running IMO.

Consider this: my Corvette's first fan came on at 225F and the secondary fan at 235F! And even then GM told owners, "it's designed to run that way."

Unrelated, but since you live in Champasak you may know something about this: on a visit there this past January we had reservations at the Grand Hotel, but when we arrived we were told that my Thai nephew could not stay there because of a hotel policy barring Buddhist monks (which he is). So we moved over to the Palace Hotel which had no such policy and had a nice stay. Do you know what's behind this strange, stupid (and in the US certainly illegal) hotel policy? That the city even allows such discrimination -- in a Buddhist country! -- seems very odd.
 

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Hi Mike,
Thanks for your thoughts.
If allowed I differ from your opinion as I understand that thermostats restrict water flow even when fully open.
Also, the temperatures t which the Thermo switch actually engages is not 100% clear as I read in some documentation that the standard switch already opens at 88 C rather than around 90.
I have replaced the radiator, hoses, fan (standard) and filled with Toyota car coolant (as EI is not available in Laos or Thailand).
Enormous improvement still coming to a stop and idling at a traffic light (of which we luckily only have a few) the temps get back into the red and warning sign of over temperature comes on.
An Indian adventurer riding from Bangalore passed Luang Prabang on the way to Kuala Lumpur had fitted double cooling fans which is another option.
Our day temperatures here now are 37C and I need better cooling for the bike.

I don't think it will help. The thermostat is fully open at 96C, while the fan switches on at 96C and off at 90C. Those are actually pretty low temps by motorcycle standards (at least by the ones I have owned) and I suspect that the fan cycling on and off so frequently may be the reason many owners think their bike is running overly hot. The temp gauge also seems to encourage riders to think they are overheating too easily -- if the gauge had actual numbers instead of just bars I think we would see that the condition is not that bad. I know that when my fan comes on it drops the temp fairly quickly, and if it can get it down to 90C that's cool running IMO.

Consider this: my Corvette's first fan came on at 225F and the secondary fan at 235F! And even then GM told owners, "it's designed to run that way."

Unrelated, but since you live in Champasak you may know something about this: on a visit there this past January we had reservations at the Grand Hotel, but when we arrived we were told that my Thai nephew could not stay there because of a hotel policy barring Buddhist monks (which he is). So we moved over to the Palace Hotel which had no such policy and had a nice stay. Do you know what's behind this strange, stupid (and in the US certainly illegal) hotel policy? That the city even allows such discrimination -- in a Buddhist country! -- seems very odd.
 

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Posting here rather than start a new post as it is related.
Has anyone here on the forum (in the hotter countries) ever ditched the thermostat in order to improve the coolant flow and improve the cooling?
Temperatures here (Southern Laos) hardly ever get below 20C and I think (taking it easy the first few km's) we do not need the thermostat.
Anyone that has tried this, I'd be very happy with your experience and possible T piece you have used.
Trying to keep cool ;)
If I lived somewhere as warm as you I'd certainly try to eliminate it as you are suggesting.
I think you will need to look carefully at the coolant circuit - you want the coolant to pass through the radiator only, so perhaps one connection to the T-piece will in fact need to be blanked off, and the other 2 hoses just joined? If you just have an open T piece this could stop flow through the radiator altogether :eek:
Have you thought about a bigger radiator? This gives the benefit of a bigger cooling area and also more coolant in the system. Has anyone tried to add an oil cooler?
 

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The radiator on my single-cylinder, 40hp, 390cc Duke is very close in size to that on my former 70hp, 650cc twin-cylinder V-Strom (I know that because I transferred a radiator screen guard over from the 'Strom to the Duke and it fit perfectly). The V-Strom was remarkable in that it never got above mid-range on the temp gauge no matter how long sitting at idle or viciously flogged on the hottest days. I never once saw an owner complaint about temps, only praise that they NEVER got above three bars on the five-bar scale. In fact the radiator on my former Vulcan 1600 was only slightly bigger than the Duke's, but that one DID heat up quickly at idle. Still, the temp came right down when the fan kicked on, indicating that the radiator capacity was at least marginally adequate for that honking big twin.

So the problem -- if indeed there is one -- must come from something else. And, honestly, I have not experienced an overheating problem (for the bike!:D) even in summer temps here that often get well over 100F (38C). When the weather heats up I will put an IR temp sensor on the engine to see exactly HOW HOT it gets when the gauge is pegged and the fan running. If 100C or under I don't see any problem at all.

An oil cooler would be nice insurance, but finding space and plumbing it in might be a challenge.
 

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Thanks, AndyB and Mikebet for your thoughts and theory.
All these considerations have crossed my mind and have been considered.
The radiator (which is brand new) has made a big difference as the former one was blocked with mud/sand/little stones right at the centre where the fan sits and tries to suck air through a solid surface was not possible.
Fan also has been replaced by a new one and the hoses are the orange silicone/rubber type now claiming a better flow.
I am not worried about the operating temperature while moving (over 30 km/h) the problem starts when standing still and idling.
With the fan sucking full time (and thermostat fully open) temps keep climbing to the point where I switch off the engine.
An oil cooler will be too much re-manufacturing and as far as I know has not ben done before.
An earlier engaging thermo-switch might not be the solution as with the fan running all the time temps still go up.
Engine runs fine otherwise and no other issues than the temperature in these conditions.
At the moment day temperatures are 37 C and climbing and I plan a trip through southern Laos.
My question is; has anyone experimented this before (only running through the radiator)?
 

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Thanks, AndyB and Mikebet for your thoughts and theory.
All these considerations have crossed my mind and have been considered.
The radiator (which is brand new) has made a big difference as the former one was blocked with mud/sand/little stones right at the centre where the fan sits and tries to suck air through a solid surface was not possible.
Fan also has been replaced by a new one and the hoses are the orange silicone/rubber type now claiming a better flow.
I am not worried about the operating temperature while moving (over 30 km/h) the problem starts when standing still and idling.
With the fan sucking full time (and thermostat fully open) temps keep climbing to the point where I switch off the engine.
An oil cooler will be too much re-manufacturing and as far as I know has not ben done before.
An earlier engaging thermo-switch might not be the solution as with the fan running all the time temps still go up.
Engine runs fine otherwise and no other issues than the temperature in these conditions.

At the moment day temperatures are 37 C and climbing and I plan a trip through southern Laos.
My question is; has anyone experimented this before (only running through the radiator)?

You can remove the thermostat and it may give you marginally more circulation, but not much. The only function of the thermostat is to speed up the warm-up process from a cold start, and maybe to keep temps up into the normal range in very cold ambient conditions. But I'm still curious as to your definition of running "too hot." Are you actually getting the "high coolant temperature" warning message on the gauge screen? I don't know about this bike, but many ECU-controlled engines go into a "limp home" mode when temps get too high and before any damage is done (Harleys cut out one cylinder, I think).

It's very easy to wire in a manual fan switch so you can turn it on whenever you want before the auto switch kicks in. I did this on both the aforementioned Corvette and the Vulcan 1600. I routinely flicked it on in slow, heavy traffic or when stopped at a light. Was it necessary in either case? Probably not, but like you I obsessed a little watching the temp gauges climb. I have not found it necessary on this bike. You can't be too careful about overheating, of course, so you have to do what you have to do. Nevertheless I still think that a lot of temp regulation consternation is caused by that multi-bar gauge calibrated to stay in what appears to be upper zone under normal operation and a fan that kicks on at (by motorcycle standards) very modest temps. Remember, they ride this bike in India where it gets a **** of a lot hotter than your part of Laos, and where traffic often moves at the pace of an oxcart.

Of course, synthetic oil is always a good insurance policy. ;)
 
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