Optimal running temperature ?

Hi !
I own a 96 vfr. I've been dealing with a problem, some say it's not, but i say it is, maybe someone got some answers for me.

It's about engine running temperature. The temperature indicator is not rising to much, but i know that the temp sensor is calibrated lower. I've been doing some research on this.

1. The temperature of the hose going to the radiator from thermostat housing, is rising gradually, along with engine idle. (theoretically the thermostat is stuck open when doing that)
2. I took the thermostat down, put it in boiling sauce pan: it's working flauless, opens, shut's perfect, no coolant escaping.
3. I've used a multimeter, set on ohmmeter, to read resistance of the temperature sensor. it reads just like in the attachement.
4. I've covered the by-pass hole (tined), to check for coolant leakage. temperature in the radiator hose and radiator, stay's cold, not warming up gradually.

Now my questions:

1. Doesn't the by-pass hole is way to big, and so, to much coolant escapes into the big circuit, preventing the engine to warm up sooner ? For me that explains why the temperature indicator fluctuates when getting in and out of traffic.
2. Was it designed to work cooler ? If i'm guessing by the ohmmeter readings, that temperature in the engine is ~75-78 Celsius (167-172 F). Radiator hose and radiator is hot, when thermostat should open only at 82 Celsius.

I was thinking to instal the thermostat with the by-pass hole facing backwards, or cover it permanently (i know it's risky). This phenomenon was observed by another friend of mine, on a 95 VFR. he says that it's normal for the vfr, but again, i don't think so.

Any explanations ? How is your vfr work ?

 

Whatever you do don't install the thermostat backwards. If the bike holds the right operating temperature while cruising in cold weather then the thermostat is working the way it should. These bikes are known to run hot in traffic because the cooling fan does not kick on until engine temperature is way above the temperature at which the thermostat opens. It sounds like your cooling system is working properly, slight coolant flow is needed at all times to flow coolant from the engine to the thermostat to warm it up when starting from cold. If the gauge stays somewhere around the middle while riding I'd say you're good to go.

 

Ok, but the coolant passes through the thermostat, warming it up in a longer time. I've never seen a 4th gen running with temperature indicator in the middle of the scale, in cruising mode, just in traffic or going with slow speeds and high rpms.

Maybe these bikes are known to work cold, not hot like you said. The temp indicator on my bike sits like in the 56 ohm picture.

 

My 5th gen runs 168-175 degrees F under cruising conditions, the fan doesn't turn on until 222 degrees. Because of that, the engine temperature fluctuates significantly in traffic. If you think your bike is running around 170 degrees F like you stated while cruising I think everything is good. If the bike were running cold, you would likely notice spark plug fouling, poor carburetion, and other running concerns.

 

My 4th gen temp gauge is the same. It is almost never near the middle of the gauge....only a little above the Cold mark.

 

Try to feel the hose going to the radiator, see how it's warming up, gradually or instant.

 

It only takes you less than 10 minutes to work it out.

 

I'm with Slowbird on this one. Mine hovers around the cold mark only rising if I sit in traffic on a hot day.

 

Which hose? When sitting on the bike...Left side hose or right side hose?

 

With you sitting on the bike, right side panel. It's the hose going out from the thermostat to the radiator.

 

Yesterday when I left work I remebered to check right before I left.

Bike was idling for only a few minutes. Right Side hose was slightly warm....but not much. The air around my hand felt warmer.

 

Right as i suspected.
Definately, through the bypass hole is escaping to much coolant, preventing the system to warm up properly.

 

i agree the 4th gens run cold and not at an optimal temperature.

What pilot and main jets are you running?

My '96 runs cold also but it has a stupid jet kit with #42 pilots.

i started adding strips of duct tape to cover over the front of the radiator and the temp never got up to the half-way mark (between 32 and 24 ohms) until i had three strips and we had some 95 degree temps outside and i got stopped in traffic, then the thermostat opened (slightly below the 24 ohm line) and fan came on etc. When moving the temp stays down even with three rows of tape.

Also the fuel mileage will be very poor with a cold running engine, and my mileage went from low 30's to low 40's by adding the tape and getting more heat into the motor.

 

but the thermostat opens between 48 and 52, meaning 82Celsius.

the jets are stock, i'm 99% sure. If you said that by adding duct tape you mpg increased, i will try it to.

 

after taking down the thermostat several times, i can do it now in ~ 12 minutes with the panels on the bike, and not loosing any drop of coolant.

It seems that coolant is escaping from the small circuit during warmup, between the frame of the thermostat and the thermostat housing. Maybe the round frame of the t'stat is curved a bit, i couldn't notice. For fixing, i made a tiny gasket around the round frame. Now, coolant doesnt escape no more and the temperature needle is rising faster than it did. I will be post back after checking the mpg.

 

I think you're chasing a problem that doesn't exist. My VFR generally runs like your 56 ohm picture, only if I'm in traffic for a while will it go to the middle of the gauge and them the fan will turn on. Just my 2 cents.

 

Ever consider its just the gauge that reads low and the temperature of the bike is where it should be. My 5th gen runs at 170 degrees F while cruising. Whats your engine temp in degrees? The gauge on my RX7 reads low cause the sending unit is off of a different year(so is the engine) I just adjust what I recognize as normal operating temp and go on living my life...

 

I have also heard somewhere that though the guage shows low, the actual temp is normal.

i think unless you hood up a digital guage and see what the temps are actually at....you should leave it alone.

The needle on my temp guage rarely moves above the Cold mark and I still average 5.3L/100kms....and have even got as good as 4.7L/100kms.

 

I've just replaced the thermostat in my 5th gen (82 deg C set point). Cruising, it now sits between 75 C and 77 C. Before, it was more like 65C, or below on a cold day (the old thermostat was stuck open).

In case nobody has pointed it out, the bypass hose circulates the coolant in the hot galleries (this gets a more even engine temp, and reduces risk of localised boiling in the head, plus it reduces the "snap closed" effect that cold flow from the rads can cause). The bottom disc on the thermostat closes the bypass when the engine is up to temp. It's detrimental to remove it, so please leave it alone. If it wasn't needed, Honda would've left it out to reduce production costs. A bypass system is standard on all cars and bikes built now. The reason is: it controls the temp far better than the old non-bypass systems.

 

Mine pretty much stays at 56 ohm picture, on the freeway it might go a bit lower and in really bad stop and go traffic on a hot day, maybe it'll go a hair higher.

I've never had the fan turn on but maybe because it's always pretty cold where I am?