'02 VFR800 running cold

[1TallTXn]

Howdy folks, my 2002 VFR800 ain't running up to normal temps.

She's currently just shy of 37,000mi and I've had the "pleasure" of replacing 2 thermostats for being stuck open.
The last time she stuck open was a few months ago, and since that replacement, "normal" temp has been about 166F. She will on occasion reach higher temps, for example last night at 90F air temp and running in stop/go traffic it was over 200F.

assuming the t-stat was stuck open again, in under 3k mi, or simply the wrong temp, I replaced it a couple weeks ago. Only to discover that the t-stat was NOT stuck open, the t-stat was marked the correct 82C. I went ahead and replaced it but I'm still having the same issue.

Fuel mileage is down to about 31-33mpg.

no mods have been done to the engine or exhaust.

I have verified that the on-board temp gauge is within a few deg F of actual. Close enough to trust it.

Anybody got any suggestions or things to check?

This has been cross-posted to VFRD

[dukey33]

Pretty unusual for an engine to run cold and not be a faulty t-stat.

I'd still suspect the temp sensor. Look in the service manual. There should be a procedure to check the temp sensor. Might involve heating it in a pan of water and measuring the resistance between the terminal and base.

Also, an 82C (180F) t-stat is not that hot. Take one of the old ones and put it in a pan of water along with a thermometer. My Honda service manual says the valve should begin opening 80-83C, and be fully open at 95C.

[1TallTXn]

Under the cooling section of the service manual, reasons for running cold are
faulty ECT
faulty thermostat
stuck cooling fan

I've checked the ECT (no test in the SM, compared actual temp of the radiator to what the ECT said, ~2*F difference)
The T-stat is working correctly
and the fan is not stuck on.

I'll try the stick-it-in-a-pan trick.

[leadwolf]

I'd run it close to red-line all the time. That'll warm the engine up...and keep it warm.

[DFW_Warrior]

Just wondering, but how is all the other regular maintenance stuff on the bike? How new are the plugs, when was the last valve adjust, how is the air filter, have you ever sync'd the TB/carbs?

It may seem silly, but some of those things all added up together may do some funky things to the motor.

[1TallTXn]

Originally Posted by DFW_Warrior

Just wondering, but how is all the other regular maintenance stuff on the bike? How new are the plugs, when was the last valve adjust, how is the air filter, have you ever sync'd the TB/carbs?

It may seem silly, but some of those things all added up together may do some funky things to the motor.

Valve adjust was at ~20k
TB sync done at ~20k
Air filter replaced less then 1k ago
Spark plugs inspected at ~35k, looked good.
Chain was replaced at ~34k

[ed29]

I wonder if the bad mileage is a side effect of the cool running, or a contributing factor. Does the bike have only a stock ECU, or a PC-III? A very rich mixture is where I am going here. It could cause both the cool running, and obviously the poor mileage. This is only a guess on my part. reading the plugs should help tell the tale.

[1TallTXn]

Originally Posted by ed29

I wonder if the bad mileage is a side effect of the cool running, or a contributing factor. Does the bike have only a stock ECU, or a PC-III? A very rich mixture is where I am going here. It could cause both the cool running, and obviously the poor mileage. This is only a guess on my part. reading the plugs should help tell the tale.

Bike is 100% stock.

Folks on VFRD are starting to think that its running rich, which is causing it to run cool.

[DFW_Warrior]

Hmmm... a completely stock bike running rich?? Those are few and far between, and I wonder what happened to make it start to run rich if it hasn't before. A sensor that isn't working properly maybe. Could it be a different temp sensor that triggers the EFI to go off of "cold-start" mode. Maybe you are just riding around with something similar to full choke?

Just a guess, but it could be something to look at.

[dukey33]

Originally Posted by 1TallTXn

Folks on VFRD are starting to think that its running rich, which is causing it to run cool.

I think it would have to be flooding the cylinders with raw gas to get the engine to run that much cooler. You never stated what the expected normal temp is, but with a 180F 'stat, it should be 185-190.

[1TallTXn]

I'll have to look at the SM this evening to give you exact numbers, but it normally ran in the 185-200F range when it was working correctly.

I think I'll pull it apart Sunday and see if I can see anything thats out of whack.

[Skid]

Maybe a bad fuel pressure regulator? That could increase pressure on the injectors and add too much fuel, thus causing it to run cold as well.

[1TallTXn]

Originally Posted by Skid

Maybe a bad fuel pressure regulator? That could increase pressure on the injectors and add too much fuel, thus causing it to run cold as well.

I hadn't thought of that one.

[Skid]

If you do find that to be the problem and it needs to be replaced. Get the one from Turbo City. They will set the pressure more accuratly than one just from Honda. Patricia has one on her bike and it seems to work well.

[1TallTXn]

Originally Posted by Skid

If you do find that to be the problem and it needs to be replaced. Get the one from Turbo City. They will set the pressure more accuratly than one just from Honda. Patricia has one on her bike and it seems to work well.

I've heard of folks doing that mod, so if thats faulty, I'll get the Turbo City one.

[Skip Honeycutt]

I monitor the ST1300 owners website and it is common for those T stats to stick open. Don't know if the VFR uses the same one but Honda has replaced a ton of em under warrenty. Most ST owners appear to be using aftermarket replacements. Newenough.com sells one of the non Honda brand T Stats. This may be way off base but I know how it is to be grasping...

[wczimmerman]

Here's my fix when the thermostat kept sticking open on my 04 VFR:
Linky

Same solution is guaranteed to work for you, too!

[1TallTXn]

Originally Posted by Skip Honeycutt

I monitor the ST1300 owners website and it is common for those T stats to stick open. Don't know if the VFR uses the same one but Honda has replaced a ton of em under warrenty. Most ST owners appear to be using aftermarket replacements. Newenough.com sells one of the non Honda brand T Stats. This may be way off base but I know how it is to be grasping...

The ST1300 uses a very similar T-stat and I tried one in the VFR, but the ST's has a weep hole in it that allows too much water for the VFR to maintain temp.

Originally Posted by wczimmerman

Here's my fix when the thermostat kept sticking open on my 04 VFR:
Linky

Same solution is guaranteed to work for you, too!

I think I'll take stuck open t-stats to failing rear shocks

I do really like the SV's, its just my budget says its cheaper to fix this one then get anything else.

[pacman]

Does the VFR have the wax unit thingy to control the warm-up process? Here's a description of how it works from cbrxx.com

The "automatic first idlle wax unit" is shown in the FSM on page 551. It is connected to the engine cooling system by two hoses. When the coolant is cold, the wax contracts and a spring pulls an actuator which opens the idle air valves in the throttle bodies. As the engine (and coolant) warms up, the wax expands against the actuator and closes the bypass valves. The ecm will adjust fuel ratios accordingly.

The general idea is if the wax is old and "worn out" it won't expand and contract as it should, causing the ecu to stay in the rich warm up mode.

The first time I heard about this thing I was pretty surprised. Wax in a modern motorcycle part?

[1TallTXn]

Originally Posted by pacman

Does the VFR have the wax unit thingy to control the warm-up process? Here's a description of how it works from cbrxx.com



The general idea is if the wax is old and "worn out" it won't expand and contract as it should, causing the ecu to stay in the rich warm up mode.

The first time I heard about this thing I was pretty surprised. Wax in a modern motorcycle part?

yes, it does have that "wonderful" method of controlling a cold start.
I wondered if I accidently bent the rod connecting that wax unit to the rear TBs, I'll check that rod and the wax functioning when I get a chance to take it apart.