Beating a dead horse - thermostats and 5th gen operating temperture

I’m likely beating a dead horse here, but I can’t find a true consensus on older postings. On cool days, say 75 F (22 C) or less, what does your 5th gen VFR coolant temperature gauge settle at once you reach steady cruising on the highway or interstate? With the temperature sensor in the front head, one would expect something a little above thermostat opening temperature. The issue is that our VFRs have the bypass circuit in the thermostat housing that always allows some flow to the radiators irrespective of thermostat state. That flow path deosn't seem insignificant in diameter. It’s hard to know how much cooling that accomplishes without applying some engineering rigor. I figure the best way is to ask the members what they are seeing.

Probably the most useful responses would be those stating ambient temperature along with coolant temperature at that ambient temperature once you reach steady state while cruzing. Given the high failure rate of our thermostats, the highest confidence responses will be from those who recently replaced (say in the last few years?) their thermostats.

I haven’t replaced my thermostat since I’ve purchased the bike (this March) and being the third owner, I don’t know the history of what has occurred regarding thermostat replacement. I suspect I’m in that grey area temperature-wise and suspect mine isn’t stuck, but doesn’t fully close (it reaches approximate thermostat temperature in ~3.5 miles of low traffic conditions on warm, say 80+ degree, days). Here are my steady state observations:

Steady speed = ~45 mph, ambient temperature = 88 degrees F -> temperature gauge = 181 degrees F

Steady Speed = 60 - 65 mph, ambient temperature = 73 degrees F -> temperature gauge = 165 degrees F

Thanks.

- Walt

 

I don't know my temps off hand, but I do know riding around with only the front upper fairing on drops temps considerably, even in 90°+ days here near Nashville, including all of the humidity, (if that even makes a difference to a radiator)

 

My '99 5th Gen (with a new thermostat installed a year and a half ago) runs in the low 190s in those conditions (about 75 degrees outside, cruising on open roads).

 

My 5G never gets below 77°C no matter how cold it is outside (never gets below 3°C here).
On hot days, 36°C to 46°C, it sits around 86-88°C as long as I'm moving over 80kmh in clear air (no cars in front of me).

 

I went out for a long ride on the weekend and it was approximately 7c ambient temp. My 5g sat at between 58 - 62c coolant temp doing 110 km/hr for about half an hour. I consider that to be a bit low! When the outside temp is closer to 20c then it will sit around 70 - 75c, rising in traffic.

Sent from my SM-G950F using Tapatalk

 

I think you need a new thermostat.

 

I'm close to you on my 5th gen.
Steady 45mph on at about 185 F
Steady 50+mph 174 F.

Also, if it's hot out and I'm under 35mph it's hitting 210-220F. It cools better sitting still with the fan on in hot conditions. Not enough air flow to overtake the fan at low speeds.

 

I finally got around to doing the work to check/replace my thermostat in my 1998 VFR800. Removing the throttle body assembly required lots of lube and lots of mechanical persuasion. The thermostat was failed open (about 1/4" at room temperature). I tested the new thermostat prior to installing to make sure it worked per the spec and it did (it opened in the mid to high 170's F). With the new thermostat, it warms up a lot faster. I went out Sunday night and maintained 70 mph on US50 between Bowie, MD and Annapolis, MD. Ambient temperature was 39F. My dash gauge varied between 168F and 169 F when I held the aforementioned steady state speed. I guess the bypass hose to the radiator is just enough flow to allow some measurable cooling to take place which is why the gauge temperature is less than thermostat temperature (assuming the dash gauge is somewhat accurate).

 

The water temp is measured at the head, while the thermostat opens with coolant temp after it has left the head, there is always going to be a slight difference.
Even on a hot 36°C day at speed mine stays at around 78°C