Poor fuel mileage

Joined
Aug 8, 2015
Messages
471
Location
CT USA
Bike
07 ST1300
My average mileage has been reading in the high 20's for a while. The bike is an 07 with about 15,000 miles. Not a lot.
So I read up on it and figured the first bit of advice would be change out the t stat. So I ordered a honda replacement and O ring. Dug in and did it. Still waiting for my jug of honda type 2 antifreeze and some bolt's and rivets and things. So the plastic is still off.
Anyway..everything looked brand new. The old thermostat looked just like the new thermostat and the GREEN fluid looked brand new. The overflow bottle spotless.
IF the old Tstat was good, what else should I look at I wonder. I DID recently and finally see evidence of a slow warmup but only once it seemed to take an extra minute or two to get to 3 bars. Took maybe a half mile farther to get to 3 bars.
I have flushed system with distilled water. The black paint was inside the radiator outlets but perfectly intact. I removed it as prescribed. Tstat ground is clean and VERY tight.
Any ideas?
 
Joined
Jul 15, 2014
Messages
26
Location
Rochester , ny
Bike
2006 ST1300,2000 VFR
If it isn't your thermostat...check the filter. I bought my '06 last year and the filter made a nice condo for some mouse.
 

st11ray

2006 ST1300
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Jul 29, 2007
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charlotte, nc
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'06 ST1300
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7189
Was your temperature bar bouncing back and forth between 1 and 3 bars when riding in temps below 50?
 
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JimGregory
Joined
Aug 8, 2015
Messages
471
Location
CT USA
Bike
07 ST1300
Filter is brand new. Old filter looked almost new (sadly). Temp bar has always been rock steady 3 bars.
I don't KNOW that it isnt the thermostat. I cant ride till sometime later this week when parts get in, or not for months if the snow fly's.
I have never checked miles against fill up either. Maybe the MPG is way off? Seems it degraded slowly though. I have seen it in the 40's early on. This was my first season with the bike.
I wonder how the bike knows the MPG.
 
Joined
Aug 11, 2014
Messages
838
Location
Lake Zurich, Illinois
Bike
04 ST1300
my temp bar goes back and forth between 3 and two when riding below 50. Does that mean the T stat needs replacement. I get about 40 mpg hwy at roughly 75 mph.
 
Joined
Feb 6, 2005
Messages
756
Location
Seattle area
Bike
2016 FJR1300ES
STOC #
265
my temp bar goes back and forth between 3 and two when riding below 50. Does that mean the T stat needs replacement. I get about 40 mpg hwy at roughly 75 mph.
Probably. It should stay at 3 bars once warmed up at just about any temp. Probably on it's way out.
 

ToddC

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Feb 2, 2015
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60
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Seven Bays Wa
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2006 ST1300A
my temp bar goes back and forth between 3 and two when riding below 50. Does that mean the T stat needs replacement. I get about 40 mpg hwy at roughly 75 mph.
In my opinion....Yes. temp should be rock steady at three bars. I had a stuck stat on two of my bikes. Once while riding in 32 degree weather I lost all bars and the choke set up and it really sucked down the mpg.

ToddC
 

dduelin

Tune my heart to sing Thy grace
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Feb 11, 2006
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Jacksonville
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GL1800 R1200RT NC700
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STs run 3 bars after a few warm up miles no matter the ambient temperature. Never 1, never 2 with a healthy thermostat.
 
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JimGregory
Joined
Aug 8, 2015
Messages
471
Location
CT USA
Bike
07 ST1300
We need a "What to do if your mileage sucks" sticky. Something along the lines of:
First: Check for rat's nest in the air filter.
Last: Change thermostat and coolant.
And everything in between. Starting from easy and ending in NOT easy. I don't know the in between part yet.
I have done "First" and "Last". Maybe I fixed it. Or maybe it wasnt broken. Maybe an in-accurate dashboard and mostly round town riding is the culprit. I know I don't ride like a grandma, but I bet there are grandma's faster then me!
I have got a spare 5 way connector. Extra vacuum line. Plastic hemostat's. Sticks. Maybe that's next? I would like to check all the stuff that needs the tupperware off while the tupperware is off.
Have I mentions the bike runs pretty dam perfect?
What does your all's dashboard say for around town riding at a sporting pace?
 
Joined
Sep 4, 2013
Messages
8,108
Location
Cleveland
Bike
2010 ST1300
My annual mpg runs from 39 to 43 (depends how many gas receipts I lose), but I think its real world close to 40+. Around town the instantaneous mpg runs around 20 - 30, with the average showing in the high 30s.

Sounds to me like you have the problem solved - but unfortunately, unless you take the bike out for a spin with no tupperware you won't know until its back together. This is what I would do: Put the mirrors back on, use wire ties to hold any loose wires/pieces tight to the bike, and head for the nearest gas station. Fill the tank carefully up to the lower rim of the filler neck with the bike on the center stand. Note as closely as you can where the level of the gas is and zero a trip odometer. Go out for a quick spin of at least 40 miles. Watch the gauge reading, and return to the same gas pump and fill it up to the same level as before. Ok, you know the miles, you know how much gas, so now do the math and you should see if the problem is solved - total time, maybe two hours. Return home and add stabil if you're laid up for the winter and put it together or dig deeper.
 
Joined
Mar 20, 2016
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1,201
Location
Auckland, New Zealand
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2005 ST1300
STOC #
8901
You can of course test your thermostat; dangle it in a pot of water (when your wife is out unless she is very understanding) and slowly bring the temperature up. If you have an immersion thermometer so much the better. At around 80C the thermostat should begin opening and by 95C it should be wide open (about 8mm). Very easy to visually see the movement.
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Another possible cause of high fuel consumption is related to the fuel pressure regulator. Basically the fuel pump is designed to supply excess pressure and the regulator controls the pressure in the fuel rails. The regulated fuel pressure is controlled by an intake vacuum signal so that the relative pressure at the injectors remains constant even when the intake vacuum changes. A couple of possible faults are a breach in the vacuum line to the regulator, or failure of the diaphragm in the regulator. The former will lead to higher than normal pressure at the injectors so more fuel per injector cycle. The latter can allow fuel to be dragged straight into the intake down the vacuum line.
 
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JimGregory
Joined
Aug 8, 2015
Messages
471
Location
CT USA
Bike
07 ST1300
My annual mpg runs from 39 to 43 (depends how many gas receipts I lose), but I think its real world close to 40+. Around town the instantaneous mpg runs around 20 - 30, with the average showing in the high 30s.
Wait..if your around town instant is 20-30..then my average is right in your ballpark I would think.
Dunno how the around town average could be high 30's. You mean overall average?
 

Blrfl

Natural Rider Enhancement
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Aug 24, 2005
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55
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Northern Virginia
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Fast Blue One
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4837
I wonder how the bike knows the MPG.
Not much to it, really. The ECM takes the same information to it uses to drive the speedometer and odometer and uses it to calculate miles. Based on fuel pressure, the area of the holes in the injector and how long it holds the valve open, it can calculate gallons. A little math over a few feet and a few squirts of fuel and you can calculate miles per gallon.

--Mark
 

Byron

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Mar 3, 2006
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KY
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You didn't mention how you ride. What kind of mileage are you getting out of your tires? If your tires are wearing out in under about 8K miles you might what to look at your right wrist as a possible cause. :D
 
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JimGregory
Joined
Aug 8, 2015
Messages
471
Location
CT USA
Bike
07 ST1300
You didn't mention how you ride. What kind of mileage are you getting out of your tires? If your tires are wearing out in under about 8K miles you might what to look at your right wrist as a possible cause. :D
I actually did mention how I ride, and it being a possible cause. I think I said "Sporting Pace". I ride faster then slow people and slower then fast people.
Also ALL my road trips are 2 up. Probably around 330 lbs plus gear and luggage.
 
Joined
Apr 16, 2010
Messages
1,263
Location
Rochester Mn
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2014 FJR ES 2009 WEE
I don't know if you have a seasonal variance, but at least here in Minnesota we have winter formula gas and then summer formula....something about pollution rates whatever, and amount of ethanol etc....but my experience is at least 10% and often times 15% less fuel economy when that's what I have to use.....but it beats just watching out the window at the snow and ice.....ride well, ride safe...........ff
 
Joined
Aug 1, 2011
Messages
39
Location
california
Bike
04 st1300
STOC #
8455
Do you go to the same gas station always? Tire pressure? My mileage was down due to tire pressure and winter gasoline. Oh and for sure check the dragging rear brake!! Just had to do a rebuild of the front proportioner was full of gelled brake fluid.
 

mlheck

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Feb 12, 2006
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Ft. Wayne, IN
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'18 BMW K1600GTL
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664
I will be following this thread as I also am having an issue with my fuel mileage. I have an 05 with 70k miles and it has always averaged 40-42mpg in combined riding. Last year it dropped to 36-38mpg. I also plan to change my thermostat even though it holds a solid 3 bars at all times. Air filter was cleaned last year. Might be an issue there, but haven't pulled plastic to double check it yet. I'm running a Turbo Tom fuel pressure regulator but might put stock one back in if I can find it.
 
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JimGregory
Joined
Aug 8, 2015
Messages
471
Location
CT USA
Bike
07 ST1300
Do you go to the same gas station always? Tire pressure? My mileage was down due to tire pressure and winter gasoline. Oh and for sure check the dragging rear brake!! Just had to do a rebuild of the front proportioner was full of gelled brake fluid.
Variety of gas stations. Tire pressures I am very good at keeping to 42 cold. I have TPMS. Rear brake is behaving properly. I have rebuilt the linked bit but it wasnt needed. Rear tire mileage unknown as it was there when I got the bike. I have replaced it though.
Mlheck your reduced average of 36 to 38 is fully 10mpg or so more then mine and I am questioning whether mine is normal? I think it is not normal and I surely have an issue. Time will tell it the Tstat fixed it.
 
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