Poor fuel mileage

OK, So I received another new thermostat and decided to do a little testing before I installed it. I used two different thermometers at the same time, and averaged the results of the two. This is what I found, Thermostat starts to open at 180. Reaches fully open at 190, about 1/4". Starts to close again at 180, but doesn't reach fully closed til 170. The 170 closing mark kind of surprised me. What have others found if they did this? I'm sure the HSM gives specs for this, but in middle of two other projects and don't have time to look it up right now.

OK, HSM says it should open between 176-183, so I guess it works as it should.
 
Last edited:
The 2nd replacement thermostat did the trick. Back up to 42mpg. I made sure to order it from a different parts house, hoping to get one from a different stock. It would be nice if we could find a off the shelf replacement for these as the Honda ones seem to be hit or miss.
 
Woonjas said:
I know there's a thread here somewhere that lists an off-the-shelf Gates thermostat available at just about any autoparts store.
Click to expand...

That's for the 1100. There's no off-the shelf replacement for the 1300; if there was, we'd have found it by now. Back when Turbo Tom was selling ST parts, I'm pretty sure the thermostats he was selling were custom-ordered.

--Mark
 
Blrfl said:
That's for the 1100. There's no off-the shelf replacement for the 1300; if there was, we'd have found it by now. Back when Turbo Tom was selling ST parts, I'm pretty sure the thermostats he was selling were custom-ordered.

--Mark
Click to expand...

If I remember correctly, he posted on here somewhere that he found a VW thermostat that fit.
 
So, Jim, did you get your problem solved? Was it a sticky thermostat. Last time I rode my 05 1300, my temp gauge was going between 1 and 3 bars at 42F outside. I have suspected a sticky thermostat last spring riding in the 40s and my average mileage was dropping. I am going to change the thermo and coolant and hoses. Any recommendations while I am in there?
 
I haven't read all the posts here as there are quite a few so sorry if this is repetitious.
I got a 2006 ST1300 at the end of October and rode it 265 miles home on a day that has been our only 'winter' weather here so far. Low temp at the end of the trip was mid 40's with light rain. The bike performed problem free, maintaining three bars on the temp indicator for the entire trip. Rode it around in town while my filters and feel-good parts were on order. Last week I got around to changing the coolant and flushing out the system. Did this with a cold engine. When I refilled the radiator, I started the bike and watched for the thermostat to open. Coolant immediately began flowing, indicating a stuck thermostat.

My only comment after this life story is that the thermostat can stick open and the temp gauge indicate normally in cool weather.

There is the possibility that it stuck during my last ride.

Addendum 12/8/2017.....
Replaced a very new looking thermostat which was obviously stuck open. I was able to get it to move just a little, the movement felt gritty. It could have easily stuck closed on a ride. Installed the new Honda thermostat and o-ring. Ran the bike up to temp several times until it the new thermostat functioned and the fans came on. This run, cool, run cycling took all afternoon but I convinced myself that the new part works and that there are no coolant leaks.

A big discovery is that someone recently replaced all the coolant hoses and clamps.

Checked everything visible and closed it up. I had also ordered an assortment of the little plastic fasteners just in case. In this case, I used at least half of them.

Woke up to 23 deg F this morning so will probably give it a ride tomorrow.
 
Last edited:
When I purchased my 2005, the temp gauge would immediately go to three bars even though the engine was stone cold. The previous owner said the MPGs were in the low to mid 30s, so I suspected a bad thermostat. I replaced it and now it starts at zero bars and goes up a bar at a time until it hits three bars when it's fully warmed up. Now my MPGs average in the mid 40s.
 
Tacoland said:
So, Jim, did you get your problem solved? Was it a sticky thermostat. Last time I rode my 05 1300, my temp gauge was going between 1 and 3 bars at 42F outside. I have suspected a sticky thermostat last spring riding in the 40s and my average mileage was dropping. I am going to change the thermo and coolant and hoses. Any recommendations while I am in there?
Click to expand...

Hi Taco.
Ya I guess my problem is solved. I run 3 bars always. All I did while I was in there was look around and snug up some hose clamps. Might have done other stuff but I don't remember! I only have about 16000 miles on my 07 so everything looks pretty new. I know my idle adjuster is stuck though. Wish I addressed that when I did the starter valve sync.
I think my MPG's are not what others report, but I am always set on average and I do mostly back road riding with a heavy hand. I enjoy the power this bike makes.
 
Oldbikefixr said:
I haven't read all the posts here as there are quite a few so sorry if this is repetitious.
I got a 2006 ST1300 at the end of October and rode it 265 miles home on a day that has been our only 'winter' weather here so far. Low temp at the end of the trip was mid 40's with light rain. The bike performed problem free, maintaining three bars on the temp indicator for the entire trip. Rode it around in town while my filters and feel-good parts were on order. Last week I got around to changing the coolant and flushing out the system. Did this with a cold engine. When I refilled the radiator, I started the bike and watched for the thermostat to open. Coolant immediately began flowing, indicating a stuck thermostat.

My only comment after this life story is that the thermostat can stick open and the temp gauge indicate normally in cool weather.

There is the possibility that it stuck during my last ride.
Click to expand...

I am PRETTY SURE I witnessed the same thing on my bike. I believe it's normal for SOME coolant to flow instantly. Maybe there is a bypass or some such thing. Perhaps an expert will weigh in. I THINK what you see flowing is not going through the radiator cooling fins. I am fuzzy on this though. Getting old I guess. I wouldnt replace that Tstat just yet. For me it was like a "thermostat go round". But my first replacement I managed to install improperly and so on.

OK cut and pasted below from last winters thermostat odyssey. These were my observations then, posted earlier in this thread.

It should reach 3 bars within a few miles no matter what the ambient temperature. Colder ambient means a bit longer wait. This is a fact. There IS coolant circulating instantly from start. It goes IN the starboard side top of the radiator, and out the starboard side bottom, so not running across the fins, but it will still cool a wee bit with very cold air temps. Enough to make 3 bars take a bit longer to achieve. I ride with temps into the 20's.
When the thermostat opens it dumps hot water in the top of the port side radiator, across the cooling fins and back into the motor from bottom starboard side.
All you REALLY have to know is, if it ever goes from 3 bars to 2 bars, you should fix it. If it take a long time to get to 3 bars, you should fix it.
 
Last edited:
Tyre pressures? Tyre pressure gauge accurate? Brakes dragging?

These are also things to check
 
Last spring on a week long ride, a lot of it high RPM spirited riding, I averaged 42 MPG. There was also about 500, 80 MPH highway miles mixed in with the 1500 total miles. In the fall on a similar, yet mellower ride with the wife on the back I averaged 35 MPG. On a few short rides this spring I am still seeing 35. I started the bike the other day in the garage and saw 1 bar after a minute and a half, 2 bars at just over 2 minutes and 3 bars at just over 3 minutes of idleing. The temp in the garage was 62 degrees.

Is it possible my T-stat could be on the way out?
 
That temperature behaviour is similar to mine, which I believe to be normal. If your thermostat was dodgy I would expect only 2 bars with possible skips between 2 and 3 bars.
 
Fawlty said:
That temperature behaviour is similar to mine, which I believe to be normal.
Click to expand...

This is my experience too. I haven't timed it but idling in a garage and taking ~3 minutes for three bars seems typical for me. I'm usually on the road by 2 though so don't have a lot of data points.
 
Fawlty said:
That temperature behaviour is similar to mine, which I believe to be normal. If your thermostat was dodgy I would expect only 2 bars with possible skips between 2 and 3 bars.
Click to expand...

ST Gui said:
This is my experience too. I haven't timed it but idling in a garage and taking ~3 minutes for three bars seems typical for me. I'm usually on the road by 2 though so don't have a lot of data points.
Click to expand...

I thought it's been normal. I've never seen it do the 2-3-2-3-2 bar dance. Just trying to account the drop in MPG. Bike runs great, recently tuned. Haven't had a decent enough ride yet since the sync.
 
Riding 2-up is going to have an effect on MPG, but a 7 MPG drop sounds a bit out of range, unless the tire pressure isn't up to snuff.
 
Is the rear disc a lot warmer than the fronts? Possibly an SMC in your future or maybe just some less than perfect gas you picked up.
 
Don B said:
Riding 2-up is going to have an effect on MPG, but a 7 MPG drop sounds a bit out of range, unless the tire pressure isn't up to snuff.
Click to expand...

My thoughts too.

Andrew Shadow said:
Is the rear disc a lot warmer than the fronts? Possibly an SMC in your future or maybe just some less than perfect gas you picked up.
Click to expand...

I hope to get a ride in this weekend. I've got a laser thermometer I'll bring along and at some point stop and check. To be honest I think I would feel a dragging brake and haven't noticed one.
 
You must log in or register to reply here.
Back
Top Bottom