Thermostat issue?

41 degrees F  at my house this morning, my 95 starts right up and a couple of miles later I am rolling down a local road at 80+, all good, runs like a champ as usual

about 12 miles later I notice the temp needle still hasn't come off the peg, I stopped for a school zone and it climbs up a needle width and then drops right back

down when I start to speed up.

My first guess is thermostat, second guess is temp gauge.

Any thoughts from the more experienced owners?

Thanks

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In the 19 years I had her, redslut's thermometer would hardly move. Most of the time. Only on say 26C+ days and giving it some welly/ride stop go traffic would it move over the half mark.

The 4th gens are known for this and I never worried.

Some added a resistor? to make it respond better I recall.

As long as the fan kicks in when needed you ate good to go.  Thermostat testing procedure is in the manual i think (never bothered myself)

Ok Dutch, thanks for that.  It ran as if it was up to temp so I wasn't going to jump right in.  After my last Ducati, (999) which spent most of its time over 230 degrees and saying it was, this is a big change to be able to idle in traffic at OAT of 95 degrees and not be concerned.

Duc sure was pretty though

Thanks!!

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My '90 was like this when I bought it - actually I am not 100% positive the needle moved that single needle width or not, but I think it did. Anyway, consensus was to replace the temp sender - that it was a common issue. Sure, enough, that fixed it. Normal readings are now way below half range at about 25-30%.

Mine was doing the same. I was doing other stuff so I drained the coolant, flushed with water, changed the thermostat, pulled and wiped off the sensors. After I refilled the system I taped the temp sensor that came with my multimeter to the hose on the right side of the bike. It came up to 186 or so and sat there, the fan would kick on and off.

Great idea, I will do just that.  I have always thought this bike was running real cold because of the gauge but it runs like a fully warmed up bike

Thought I would jump in here; on my '97 the temp gauge needle is normally about a quarter up when moving at speed, moves further upward when in traffic and the fans come on.  In other words, the needle moves  a lot and I think reflects the coolant temp accurately.  This is the end of my 3rd summer with my VFR and temp gauge has always been this way.  Of course when riding at air temps of 95+ F...the coolant does have to work.

All VFR750's are like this. It's not until you've been riding it hard for a while then end up in London city center style traffic that it gets to the half way mark and the fan kicks in. I wasted a load of money on my first VFR750 thinking the thermostat was an issue...nope, wasn't, just the way the bike is.

I honestly reckon we could get rid of the oil cooler and there'd be no issue. Might run mine for a season without one and see how it goes.

bykemike 41 degrees F  at my house this morning, my 95 starts right up and a couple of miles later I am rolling down a local road at 80+, all good, runs like a champ as usual
about 12 miles later I notice the temp needle still hasn't come off the peg, I stopped for a school zone and it climbs up a needle width and then drops right back
down when I start to speed up.
 
My first guess is thermostat, second guess is temp gauge.
 
Any thoughts from the more experienced owners?
 
Thanks
 
 
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Honda thermostats like to stick open.  

Ciao,

If it's the original thermostat, just replace it.  Should be a piece of cake.  

Your coolant temp should be around 174 degrees in normal riding and cool temperatures.  On really hot days it may get to 185-190.  220 degrees idling in traffic with fans on.

I think there's a bit of exaggeration going on here. The VFR's ALL show a low needle rise, my 94 barely breaks an 8th in normal riding but hits half way on a summers day in stop start London traffic on my commute. To comfortably get at the thermostat, it's a carb off job along with a coolant replacement. I'd be very surprised if it's that and not just the normal behaviour of the engine temp indicator.

I opened the bike up yesterday and looked at what it would entail to change the t stat, thought about how well it runs and thought "screw this" there will be a time I have more apart and I will get to it but for now I would rather ride. this is our season down here, right now!

34 minutes ago, 750

I think there's a bit of exaggeration going on here. The VFR's ALL show a low needle rise, my 94 barely breaks an 8th in normal riding but hits half way on a summers day in stop start London traffic on my commute. To comfortably get at the thermostat, it's a carb off job along with a coolant replacement. I'd be very surprised if it's that and not just the normal behaviour of the engine temp indicator.

I concur. I said my '90 reads on average 25-30% after the new sender. I remember now that when I bought it the needle didn't move at all. After the last couple of rides this past week, mine does indeed stay at about 1/8th on the gauge. Oh yeah, they also all smell rich at idle. Normal.

Cheers,

Glenn

Thanks Glenn, that slightly rich smell bugs me but less and less.  This bike runs so good, never misses a beat from idle to red line, every time smooth as silk, 200 + miles per tank.

  I would rather touch nothing unless it needs it.

49 minutes ago, bykemike

Thanks Glenn, that slightly rich smell bugs me but less and less.  This bike runs so good, never misses a beat from idle to red line, every time smooth as silk, 200 + miles per tank.

  I would rather touch nothing unless it needs it.

:fing02: There ya go. The only touching it needs now is your ass touching the seat!

:beer: :beer:

Well I would never argue the wisdom of replacing something that has reached its useful life.  Especially something as important as a Thermostat.  I replaced mine after 10 years of use, even though it wasn't broken.  It required removing the Throttle Body on my 6th gen.  It was a lot of work but not difficult.  But now I don't have to worry about it for a while, as opposed to always wondering when will it fail on me....I prefer being pro-active.  I did the same thing for my Stator two years ago.  Even though it wasn't broken I knew the chances are good it was going to fail after 40k miles.  The old stator came out looking like the lower half was a fully cooked Thanksgiving Turkey!  Replacing that was also a lot of work but it was worth it and I'm especially glad I was pro-active with it.

If you suspect something is amiss, inspect it to make sure all is well.  If it makes you feel better to be pro-active about preventative maintenance, more power to you.    I agree with this kind of logic.

37 minutes ago, Rogue_Biker

  The old stator came out looking like the lower half was a fully cooked Thanksgiving Turkey!  

Next time, read the recipe more carefully, paying special attention to oven temperature and roasting time  :goofy:

Haha!  Yeah.  This was the color of my stator at 44k miles.

[image: Image result for fully cooked turkey]

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Rogue_Biker, 11/28/2017 at 8:14 PM

Well I would never argue the wisdom of replacing something that has reached its useful life.  Especially something as important as a Thermostat.  I replaced mine after 10 years of use, even though it wasn't broken.  It required removing the Throttle Body on my 6th gen.  It was a lot of work but not difficult.  But now I don't have to worry about it for a while, as opposed to always wondering when will it fail on me....I prefer being pro-active.  I did the same thing for my Stator two years ago.  Even though it wasn't broken I knew the chances are good it was going to fail after 40k miles.  The old stator came out looking like the lower half was a fully cooked Thanksgiving Turkey!  Replacing that was also a lot of work but it was worth it and I'm especially glad I was pro-active with it.

If you suspect something is amiss, inspect it to make sure all is well.  If it makes you feel better to be pro-active about preventative maintenance, more power to you.    I agree with this kind of logic.

Yeah, that's more than fair enough. But the point here is that normal behaviour with this particular breed of bike is being challenged, potentially causing people unnecessarily cost. They LOOK like they run cool, just because the needle runs about an eighth off the bottom marker does not mean it's running cool, at all!

OP here, what I hope to do tomorrow is do the test suggested by a few here, the start up with a couple of temp probes attached and see what is what.  I am hoping to see a somewhat cool radiator get hot rather all at once as the tstat opens.  I am in the AC business so I have no dirth of temp devices.

I will post results

10 hours ago, bykemike

OP here, what I hope to do tomorrow is do the test suggested by a few here, the start up with a couple of temp probes attached and see what is what.  I am hoping to see a somewhat cool radiator get hot rather all at once as the tstat opens.  I am in the AC business so I have no dirth of temp devices.

I will post results

Cool, will be interesting to see. However, if the thermostat IS broken...it doesn't really prove a thing, these bikes look like they run cool, always have, always will :)

well, very interesting, I am going to conclude I have an inoperative thermostat.

Sitting in my shop I ran it up until the fan came on at 199 deg F. That took more than 15 min.

The radiator moved up from 80 deg F to 114 deg F a minute or so after starting, I have a few images here of the degrees and the gauge position. When I am driving I never see the gauge this high, in fact I seldom see it into the scale at all,  except in traffic and the gauge tracks , to some extent, outside air temp.

Fan comes on at just over 1/2 way up on the gauge.  I would think this engine would run at least 170 degrees to be happy which would mean I would need to see a just under 1/2 gauge while running no matter what the outside temp is, I mean, that is the job of a tStat, to deny cooling unless it is called for, right?

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That last picture of the temp gauge...is that at 199 deg F?  You're measuring radiator temp?  Or Coolant Temp?

The Thermostat will not open until coolant temp reaches about 172 degrees F.  Then it will open up and is fully open around 185-190 deg F.   I would wager that the red zone on your gauge is 230 deg F.  Most liquid cooled, piston engines make the most power at 170-175 deg F.  It produces the lowest emissions at 220 deg F.  My VFR has a digital Coolant Temp reading and on cool days, running normal speeds, the bike maintains 172 deg F.  But on warmer days, lower speeds in 2nd gear, the CT can get as high as 220 before the fan kicks in to bring it down to around 210-215 deg.  

Unfortunately, on a carburated bike, you don't have any other way to verify thermostat operation without just taking out the 'stat and testing it.  ON FI bikes, if the 'stat is always open we would notice a much higher fuel consumption because the ECM will be pouring too much fuel in the engine thinking the engine is still cold....because it is.

I went with method #2.

Pulled the t-stat (30 minutes on a Gen 4) put it in the freezer for an hour and ta-daa, still wide open.  Got one coming from Partszilla.

My bike has been running too cold for maybe 4 years of its life except for the occasional traffic jam.  PO told me "I have never seen the needle come up more than a needle width"

BTW, I was reading top of radiator tank temp for ease and continuity but I checked the rear cylinder water jacket and it matched pretty close.

Last picture was 183 F, fan came on at 199F, the gauge was just over 1/2, fan shut back off at 190 in just a couple min. 

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Seb,

Make us a few of these for a 1" hose :>)

https://www.amazon.com/Meziere-WN0071-Inline-Thermostat-Housing/dp/B003NDFEC0/ref=pd_lpo_vtph_263_tr_t_2?_encoding=UTF8&psc=1&refRID=YAXKSYGJFH1N840C8TJH

they can go in the upper hose , the lower hose, what ever and you can check /change a t-stat whenever, they seem to only be available in 1.5" and 1.25" hose sizes

While I have all the big minds here :) :)....I was looking at a set of Samco Hoses for this bike, why not, right? but at over 210 USD I was wondering if anyone knows of an upgrade hose kit a little more economically priced?

Gotta ask about the Samco hoses...what's the point? You'd be better off sinking that money into suspension components (if you've not done anything already, that is)

I don't really know, I have my hoses off and they look ok but they are off and the glossy red Samcos are calling my name. I mean I am expecting my glass clutch cover to be here soon, you can see what type guy you are dealing with .  Ohlins or Ohlins like for the rear will happen soon, as well as tires.

  I think the deal with this bike is it didn't cost much at all and I really, really like it. I just like dicking around on my bikes. My business needs me to be in or around my shop most of the day and all my bikes and bicycles, tools, Keureg machine, Bose, etc is just steps from me, its a tempting situation.

  I'll bet I like it more after the engine warms up !

LOL!  So the moral of this story is, if in doubt, just replace the damn T-stat.  I kid.  But I would.  10 years is a long lifespan for that and you got your money's worth.

Go with OEM black hoses.  If you want dress up items I'd go for powder coated wheels, carbon fiber bits,  cool smoke colored windshield,  etc.

12 minutes ago, Rogue_Biker

LOL!  So the moral of this story is, if in doubt, just replace the damn T-stat.  I kid.  But I would.  10 years is a long lifespan for that and you got your money's worth.

Go with OEM black hoses.  If you want dress up items I'd go for powder coated wheels, carbon fiber bits,  cool smoke colored windshield,  etc.

 Oh, no doubt I have a new tstat is ordered for next day delivery!

Next thing I am looking for is the gen 3 8 spoke rear wheel, there is one on the classifieds right now that is perfect for me but it is always a money thing

A shameless plug for Partszilla!

  23 hours ago I posted a pic of my broken thermostat and the notice I had one ordered with Partszilla, 23 hours later, (about now) the bike is all reassembled  and I am out the door in 30 min for a 50 mile test ride this afternoon.

The order came from Partszilla so fast, it is astounding.  The local Honda dealer, who was very nice, was talking many days and twice the price. It is an internet world Charlie Brown.

I will update after a days ride as to where my temp needle is running. It would never show hardly anything while moving before

OEM hoses for older models are already NLA.  Sillycone makes more sense then (though the Chinese sets for the NC30 seem to be cheaper than OEM would be anyway).

Ciao,

Results from a thermostat change:

  Good ride, nice weather today 72ish, about 40 miles.

  Bike warmed up very quickly, off the choke sooner than usual, it seems to have lost the rich fuel smell at idle, idle much improved. 

 I had to turn the idle down at the stop I made at the 25 mile mark, seems to idle better and lower rpm, about 1100 rpm right now, holds the heat a little longer than it did (that would make sense since it is running hotter).  Based on what I have seen and some of the replies to this thread there may be a few stuck t-stats out there.  My temp gauge now goes between the brackets and stays there.

Here is where it ran the whole ride:   Based on yesterdays results it appears to be just shy of 182 deg F,

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48 minutes ago, bykemike

Results from a thermostat change:

  Good ride, nice weather today 72ish, about 40 miles.

  Bike warmed up very quickly, off the choke sooner than usual, it seems to have lost the rich fuel smell at idle, idle much improved. 

This is what I noticed as well, except for the rich smell at idle but that's another issue.

I was just rechecking it and there is still a rich smell but very faint vs. not so faint before. Just for a test I was going to block the radiator a bit to raise the temp 10 degrees or so and see if that changes anything.  I am not fixated on this but the bike is much nicer when it warms up and I may push this a little more.

Most older bikes will smell slightly rich. Mine started smelling even richer after I de-PAIR'd it, no longer burning unburnt fuel leaving the cylinder. I need to get it to a good shop with a dyno and someone experienced with carbs that can help me. I just don't see spending the $500 in setting up an AFR sensor and a Carbtune to be able to do it myself.

If your bike is carburated, it wouldn't compensate with a richer mixture even if the engine temp is low.  At least not the way I understand it.  Unless you had to keep the choke on to idle smoothly.  

Coupedupsubie, if your bike has a stock intake, your factory jetting should be right.  If you just put a "freer flowing air filter" in, and/or a freer-flowing exhaust, then all you have to do is adjust the pilot mixture screw a bit.  I'm sure your carb has these for each cylinder.  You ride the bike until engine temp is up to normal.  Let it idle, adjust the Pilot Mixture screw in (turning it in like a normal screw) until the idle gets erratic, then turning the screw back out slightly until idle smooths.  I believe this is the standard procedure for all carburators.  The only time you would need to change the main jets is when you OPEN up your air box and significantly increase the amount of air entering your engine.

yeah I agree, there should be little , if any, effects on the way a carbureted engine runs if it is running cold, the idle may be affected but, with a manual choke,  you would keep the choke on a bit to compensate for that.

  I think what I may be seeing is I was able to reduce my idle speed  (by closing the throttle plates a bit) when I brought the temperature up to where it belonged so maybe by running it with less of a throttle opening I was reducing the fuel introduced to the cylinders.  

With the previous engine temperature I had a ragged, hunting idle note and it would average about 1400, when the temp came up the idle would smooth out and get faster.  I noticed a hint of this when the idle would be smoother stuck in traffic with the temp climbing.

  This afternoon I turned the adjustment knob under the tank to bring the idle to just over 1000 and it idles there really well. 

4 hours ago, Rogue_Biker

If your bike is carburated, it wouldn't compensate with a richer mixture even if the engine temp is low.  At least not the way I understand it.  Unless you had to keep the choke on to idle smoothly.  

Coupedupsubie, if your bike has a stock intake, your factory jetting should be right.  If you just put a "freer flowing air filter" in, and/or a freer-flowing exhaust, then all you have to do is adjust the pilot mixture screw a bit.  I'm sure your carb has these for each cylinder.  You ride the bike until engine temp is up to normal.  Let it idle, adjust the Pilot Mixture screw in (turning it in like a normal screw) until the idle gets erratic, then turning the screw back out slightly until idle smooths.  I believe this is the standard procedure for all carburators.  The only time you would need to change the main jets is when you OPEN up your air box and significantly increase the amount of air entering your engine.

It has a Two Brothers exhaust manifold, well which ever I decide to run for a while as I have a left and right exit. A previous owner installed the exhaust and rejetted it because he didn't like how it ran. I have it running as good as I can for now. I do have a K&N air filter that I haven't put in yet so that may get put in before this summer. The Pilot Mixture Screw setting procedure you described it right, and pretty much standard across all carburetors.  

bykemike, 12/1/2017 at 9:50 PM

Results from a thermostat change:

  Good ride, nice weather today 72ish, about 40 miles.

  Bike warmed up very quickly, off the choke sooner than usual, it seems to have lost the rich fuel smell at idle, idle much improved. 

 I had to turn the idle down at the stop I made at the 25 mile mark, seems to idle better and lower rpm, about 1100 rpm right now, holds the heat a little longer than it did (that would make sense since it is running hotter).  Based on what I have seen and some of the replies to this thread there may be a few stuck t-stats out there.  My temp gauge now goes between the brackets and stays there.

Here is where it ran the whole ride:   Based on yesterdays results it appears to be just shy of 182 deg F,

[image: DSC_1035.JPG]

This is precisely where the VFR temp gauge sits when the bike's at normal operating temperature - how much lower was it before?! If you were on the go, making good progress without slowing down or sitting in traffic, it'd drop a bit below that. People ask about this as they assume it should be sat half way...as per any car, van, truck or (potentially) bike they've driven/ridden.

So while your thermostat was stuck open, it still doesn't prove anything in terms of this being some kind of common issue...it just shows yours was open. It's normal for these bikes to show a low(ish) temp reading in normal use. In traffic, that thing would bounce above half way and the fan would kick in as normal.

However, if people can be bothered and their bike is running odd in some way AND they're spanner capable...there's no harm in whipping it off the RC36-2 and having a look. It's a much more involved process on the 36-1 due to the daft positioning of the housing, as has been stated previously.