2003 Running too cold?

Forgive me, I searched! I have what I suspect is a stuck open thermostat on my 2003. All I've found for the 6th gen is mention of running too hot. But I know my 5th gen had a thermostat stuck open, so what the hey...

Today's trip into work (first ride on the bike), 35F ambient temp. I'd see about 150F while cruising on the highway around 80 mph. In traffic, I'd see closer to 180's. Is this too low?

 

From my observations I believe the thermostat closes at 150F and opens around 175F. So yours sounds just fine to me.

 

That's a bit of a relief! Was not looking forward to changing that out again...

 

I find my 2003 is sensitive to ambient temperatures, high temps usually occur in traffic and under 40 mph where the isn't enough air flow. Been in the 60's here lately and it runs 175-180 when moving along, but can climb to 200 at lights and slow speeds. Be aware that the VTec won't work until temps get above 168 (I believe). I have never seen temps drop to below 175 after warming up.

 

Sorry, I was converting between C and F and may have gotten mixed up. V-Tec engages above ~65C(149F), thermostat seems to close at ~75C(167F) and open at ~80C(176F). At least, when it's cold out my bike keeps bouncing between those last two temperatures.

 

Hmmm. This leads me to believe the thermostat is in fact stuck open.

 

I've been running into a similar issue. I have suspected my thermostat might be stuck open, but now that the temps have dropped off I think I am sure of it. Today after a 20 minute ride, 55 mph cruise, bike indicated 42 degrees F, i could not get the bike warmer than 138 degrees F while cruising with a stiff cross wind. I have also been getting below average MPG so it looks like I need to start doing some research on replacing my thermostat.

 

Here is a good test. Let your bike sit until it is stone cold. Over night is great! Start it up and watch the temp gauge. The temps should climb until the mid 170's. When the thermostat opens up you will see the temps tumble about 6 to 10 degrees and start to climb again. This is caused by the thermostat opening up and allowing the cold coolant from the radiators to start flowing. This cold coolant causes the thermostat to close again and the temp starts to rise again until the thermostat opens again. This will happen two, three or more times until all the coolant including what is in the radiators all becomes warm. At this point the temperatures should continue rise until your fan kicks on at about 220F.

This is most noticeable when ambient temperatures are cooler or cold. Not as noticeable when it is hot out.

Bottom Line. When you watch the temp gauge rise and you see the temps drop and rise a few times in the mid 170's to low 180's that means your thermostat is opening and closing just fine.

 

Also when you are riding in cold weather your thermostat will be in a state of flux. Opening just slightly it lets all that cold coolant in and it starts to close the theromostat. When it warms it starts to open again. When there is plenty of cold air / coolant available in winter the thermostat should hover around its opening point 176F.

The reason most cars have a steady coolant temp is because they are designed with plenty of cooling capacity and their thermostats are hovering at their designed temp usually at about 190F.

 

I will have to do that check. I just can't imagine how it's normal for it to maintain ~140 degrees while cruising in 40 degree ambient temp. Unless I have twice the radiators and wasn't aware of it. Lol

 

I haven't updated this thread recently, but short of taking the thermostat out to check, I'm convinced it's stuck open. Last week, I was out riding in the low 30's. Temp never got over 135F while moving. This is the same behavior my 5th gen demonstrated when it's thermo was shot. This is on the winter to-do list.

 

There's a obvious and traditional solution for an engine that's running too cool in cool weather: block about 1/4 of the radiator area with cardboard or tape and maybe about 1/3-1/2 of the oil cooler too. Only possible problem might be in stop-and-go city traffic (not recommended for NYC) but should be OK if the fan is working right or you're never in heavy congestion.

BY varying the width of the radiator block the running temp can be finely adjusted (within the same ambient temperature of course).

I've done this anytime i'm riding a VFR at anything below about 40F.

 

I pretty much keep the right radiator blocked off in the winter. I know my thermostat is stuck but I'll get to that when I finally park her for the winter. Mine runs about 168 degrees at a steady 65 mph without the right radiator blocked; 180 with it blocked. The only time that is an issue is if I sit in traffic too long & the temp gets up high enough for the fan to kick on....after I'm moving the airflow is fighting the fan & it's unable to cool down unless I just stop. It got up to 238 one day with the right radiator blocked & ragging it hard on back roads.

 

The whole Idea of the thermostat is to block coolant flow so the engine warms up quicker and then opens to try and maintain a constant temp. The VFR is designed to open at about 176 Deg. F. If yours is running at 168F it is pretty close to spec. With the thermostat in a different location than the temperature sending unit an indicated temp of 168 may indeed mean that the thermostat is working at 176, especially if it is a cold day. The only way to test it for sure is to put the thermostat in a pot of water with a thermometer and heat it until it opens noting the temperature when it starts to open and when it is fully open. The only problem with this is if you take it all apart and do this test are you going to put the old one back in if it checks out? My bet is NO! You'll buy a new one, test it, and put it in.

Be careful, my wife gets pissed when I boil a thermostat in a pot and use her candy thermometer to check the temps!