HELP! FAN THERMOSTAT? RC51

pohiles · 10-12-2007, 10:55 PM

Alright I just got a 2003 Rc51, about a week ago. It seemed to me to run very hot but reading this forum I learned that 240 is the high end of normal. I unpluged the fans and the bike runs quite a bit cooler! Before it would get hotter on the interstate, and now cooler. I realize this is because the fans spin the wrong way. Does any one know how to reverse the fans?? Does any one know if you can run the bike without the thermostat??? Ive got a few other bikes and none of them run this hot. Does this cause undue oil wear?? Also I flushed the radiators and put water and royal purple purple Ice. Any other Ideas or tricks, Im all ears. Thanks alot, Sam

aussie-sp1 · 10-13-2007, 4:07 AM

Gday mate, im sorry to say that these bikes do run very hot in traffic and fairly warm on the highways, more so than any other bike that i have ever seen, and this has been well documented in many magazines, my bike has reached boiling point many times and the thermo fans kick in and the temperature comes down and all is sweet again. Just cut the wires and solder them back together the opposite way of what they were and that will fix the problem of them running in reverse. You may as well leave the thermostat in there and accept they they do run hot and this will not damage the bike, otherwise honda would not have ever released them for sale. If you are really worried about the high temps, you can put your own switch on the existing wires and run the wires up and mount it next to the dash or where ever you want. Just run a wire up from negative and positive respectfully and connect it to any switch which will act as the bridging of the thermostat. Good luck mate.

robfromsc · 10-13-2007, 7:51 AM

hey man, im near augusta,ga so we have pretty close weather. my 02 gets pretty hot in traffic aswell. have had it for a week or two. try what aussie said, just wonder how it got switched?

let us know what you find!

Massimo · 10-13-2007, 9:07 PM

You could also ground out your temp. switch that turns on the fan that will make the fan run all the time. If you are in hot weather area the RC fan will run most of the time anyway. You will put more wear on the fan but that fan will keep the motor safer.

pohiles · 10-14-2007, 10:58 PM

Thanks guys. you will think im nuts but Im going to fix her and send her on her way. I need a truck bad and I own 4 bikes.

Massimo · 10-16-2007, 10:01 PM

Quote:

Originally Posted by pohiles

Thanks guys. you will think im nuts but Im going to fix her and send her on her way. I need a truck bad and I own 4 bikes.

Not the RC. It's just to cool to sell. You just don't see them anywhere.

zerogara · 11-28-2007, 12:45 AM

I am wondering now, and it is too late to go out and look for the manual and parts fische, to find out how the temp. sensor is wired and where. I have a suspicion that the temp we see on this bike is not comperable to other bikes and as "other" gauges are OFF by a bit, why not the temperature.
I read some posts of people getting hot on the highway, and that is weird unless it was already hot as they came on the hwy and they got a chance to go bleep bleep on the button and see the temp then which should eventually cool off.

I don;t think it is a matter of insufficient radiator but maybe insufficient flow related to the side mounts and air coming from the inside of the engine which is already warmed up at low speeds.

Anyway, my puzzle is whether the temp is measured front or back, left/right radiatos and whether there could be differences.

Water boils at 212, right? Ok under pressure and with coolant mixed the boiling point goes up, but I've been around engines running 190's and feel hotter than the RC at 210. So I am wondering whether it is actually running cooler than it says it does.

We need to study this problem closer I think.
Koz

9Hondas · 11-29-2007, 12:10 AM

I suppose you could take temperature readings at various places with one of those digital infrared thermometers. I've got one and next time I'm out riding will see how it compares to the bike's readings. Its pretty small and easily kept in my pocket to pull out at stoplights.

Granted it will read the temp of the surface of the radiator or whatever it "sees" in its lens (like a camera) but its pretty accurate.

vitzaa · 11-29-2007, 1:17 PM

ok first of all, drain the coolant (at the lowest hose on the throttle side)
remove the radiators and remove the fans, you can keep one off the bike and reverse the polarity and fan on the other... the way your gonna do this is by literally turning the fan blade over and tighten the nut up then put some spacers on the mounts between the fan and the radiator so that the blade will not hit the fins, then get a needle and remove the male connectors and switch them on the plug. this will work much better than just reversing polarity.

use DISTILLED water and engine ice (i think thats the one, its the red liquid). next after you fill the system, start the bike and lean it as far to the clutchside as possible and blip the throttle, this will bleed the air bubbles outta the system.

you should be good to go.

also, if your running a powercommander, make sure your map isnt lean as that will cause high temps

J-Pip · 12-03-2007, 1:35 PM

I'm new to the RC's (so new that I don't have one yet, but I'm working on that) But isn't their design to pull air from the inside out? do the fans push the air through or pull cold air in?

zerogara · 12-06-2007, 12:30 AM

They push air through, I'm sure just by looking at the aerodynamics of the fairing. So when stopped at a light, all this larking warm air around the engine gets pushed by the fans through the radiators outwards. Give it a bit of a side wind from either side and it adds to the problem. It is not very convenient to have to face up wind every time you stop for traffic

But even moving at slow speeds, under 40mph in cool 50-60'F weather the temperature goes higher. Does anyone know what temp the fans are supposed to kick in and whether this can be adjusted by a thermo switch to a lower temp?

Koz

vitzaa · 12-06-2007, 12:34 AM

actually the fan(s) blow air from the outside to the inside. which is where the problem is when your moving. reversing the fan and switching the polarity will have the fan(s) blow air from the inside to the outside

zerogara · 12-06-2007, 2:14 AM

Quote:

Originally Posted by vitzaa

actually the fan(s) blow air from the outside to the inside. which is where the problem is when your moving. reversing the fan and switching the polarity will have the fan(s) blow air from the inside to the outside

This is the second time someone mentions this, the fan working backwards and I thought he meant as most fans being behind the radiator (and flow) that this one was doing the reverse, which I thought was right! I never really checked.
I doubt that Honda was so foolish so what is the reason behind this?

At some slow speed where the flow would be about equal to that off the fan the air is just not moving and the fan would only be of use while stationary!

Strange!

vitzaa · 12-07-2007, 12:43 PM

Quote:

Originally Posted by zerogara

This is the second time someone mentions this, the fan working backwards and I thought he meant as most fans being behind the radiator (and flow) that this one was doing the reverse, which I thought was right! I never really checked.
I doubt that Honda was so foolish so what is the reason behind this?

At some slow speed where the flow would be about equal to that off the fan the air is just not moving and the fan would only be of use while stationary!

Strange!

ya the cooling is a big mess up of honda on this bike, not really sure what the reasoning is being the fans working the way they do, it cools better when the bike is sitting still (better than reversing the polarity/blade and the bike sitting still) but once its moving the OEM setup is no where close to efficiency of reversing it...

zerogara · 12-07-2007, 1:28 PM

Quote:

Originally Posted by vitzaa

ya the cooling is a big mess up of honda on this bike, not really sure what the reasoning is being the fans working the way they do, it cools better when the bike is sitting still (better than reversing the polarity/blade and the bike sitting still) but once its moving the OEM setup is no where close to efficiency of reversing it...

The fans can only work against flow up to a certain speed. Then flow will defeat the pump, and either stop or reverse it if the temperature is still high. This may happen being stopped at a few lights in a row and finally getting into a highway where it takes a couple of miles or more to bring the temperature down below the whatever cut-off temp. is for the fans!.

I even read somewhere that even lowering the front a bit more than usual disturbes the flow enough that IT causes overheating.

So is fan reversing a widely approved modification? And Honda insisted for 7-8 years in having it the other way? WHY?

rc30sp1 · 12-10-2007, 5:51 PM

you think an sp1 runs hot,you should try riding an rc30!

zerogara · 12-10-2007, 11:08 PM

Quote:

Originally Posted by rc30sp1

you think an sp1 runs hot,you should try riding an rc30!

Remember it wasn't too long ago (at least it doesn't feel like it to us youthful old farts) that almost all bikes were air cooled. They lost power as they got hotter and that is what "liquid cooling" provided, extra power even when hot. Nobody had a tem gauge then and no fan went on in traffic. Hmmm...!

Back in 72 Suzuki released a bike 750cc 3 cyl 2stroke watercooled. The first couple of models had fans, then they dumped them because they never went on. By 77 when the last ones were produced Suzuki had a stock pile of engine spare parts that weren't selling. A 2 stroke that turned 6 digits in the odometer and never had the top end or any end for that matter changed.
The bike was slow and heavy, short of a 2stroke goldwing.
Moral of the story?
The more HP/cc you get the more cooling you need, and the more wear you will have if the cooling system is inadequate. People got huge horsepower numbers out of Yamaha RD350/400s but they only lasted a weekend. When cooling came out they were happier!
True or False?
An engine becomes more efficient if it can contain the heat created and not release it into the environment. So Thick cast iron cylinders and internals that can withstand high heat is best! Too heavy of an arrangement though. So, maybe RC cylinders are too thin, and too much heat escapes!
It is the same reason we don't have turbo diesel motorcycles. Have you seen a cylinder block of a diesel as compared with a similar displacement gas engine?
It is all give and take and know what you are losing when you are gaining something. Think about it when you dump all this money into modifications. Do you know what it is you are losing? Longevity is the easiest answer.

ChrisR1982Edin · 12-14-2007, 6:20 AM

My 2004 stock RC51 runs at around 110 degrees in slow traffic.. and on average 65-76 degrees when im out on the motorway giving it some throttle... at 250kmph it rads around 85 degrees.

Im thinking of getting those carbon radiator vents that click on the side of the radiators... about 160 dollars right?

OPPRACING Products - Honda VTR 1000 SP1 RC51/ SP2 RC52 Radiator Vent street/race bodywork OH028037

160.00 USD = 109.67 EURRate = 0.6854 (inv 1.459)

zerogara · 12-14-2007, 12:35 PM

Quote:

Originally Posted by ChrisR1982Edin

My 2004 stock RC51 runs at around 110 degrees in slow traffic.. and on average 65-76 degrees when im out on the motorway giving it some throttle... at 250kmph it rads around 85 degrees.

Im thinking of getting those carbon radiator vents that click on the side of the radiators... about 160 dollars right?

85'C=185'F which is pretty cool.
Those radiator fins, apart from the aesthetics, would only be of benefit if the bike was running hot at speed, by directing and stabilizing air flow. This is not your problem or for most of us. On the other hand by adding something next to the radiator you are restricitng flow at lower speeds, I think! If in fact the fans going on suck air from outside into the engine those fins at slow moving are amplifying the problem.

The only slow speed solution I can conceive is either higher capacity or higher flow rate (although if capacity is not improved I don;t see how more flow will help much). So where can we add an additional little radiator? Underneath?

ChrisR1982Edin · 12-14-2007, 12:43 PM

There is a kit that moves the radiators to the front of the bike instead... really pricey tho!!
A few thousand I think... takes temps WAY DOWN!!!

http://www.honda-rc51.de/Radiators_front-frontview.jpg

http://img90.imageshack.us/img90/6080/dsc01622rq1.jpg

and check the top left part 2600 GBP for HRC rads...

http://img114.imageshack.us/img114/7...ingguidlb1.jpg