Driving like Miss Daisy, 34mpg and fuel gauge woes.....

Purchased the bike two weeks ago, used with 80k. I fill up and fuel gauge reads a bar low. Within a few miles it reads two bars low. It was showing two bars left and it still had 3 gallons still in it. I averaged 34mpg running 93 Octane gas, seafoam was added at fill up.

According to owners notes it has a K&n air filter, I plan on checking out the filter and airbox and cleaning the filter.

When I start the bike up thermostat warms up like it should to three bars and stays at three bars. Original was already replaced, Maybe it's going bad but it's not acting like it.

I do not know the last time the plugs were pulled or change if ever, maybe they are shot?

Oil is new, so I'm not worrying about that. Bike runs smooth, strong and sounds fine.

I'm a total newbie to wrenching and in the process of getting a Service Manual

Any Suggestions? Thanks

Guttooth71 said:

I averaged 34mpg running 93 Octane gas,

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I have a 2003 and if I drive 55/60 and do not play drag race at stop lights or signs. I will get close to 50 mpg. That is a calculated number, not what the display says. My display is at least 5mpg low. Now if i encounter a strong head or quartering wind, the mileage will drop significantly.

The gas gauge woes are an area that I have not encountered. Have you let the gauge go to the blinking state? At that point you should have about 1.3 gallons left. It will take a little over 6 gallons to fill if you stop at the next station. Someone will be chiming in on how to correct the main tank level arm to get a better feedback of fuel used.

Enjoy and with throttle management you should get mid to upper 40's in fuel mileage.

164 miles then I filled up with 4.8 gallons of fuel. Gauge had two bars left. I filled up and drove 8 miles and two bars are already off full tank.

Yes there is something wrong with the main tank sensor. 1 bar is about 1 gallon of fuel used. ABOUT. What year is yours and what speed were you averaging. Speed kills mileage.

replace the plugs. i had 26k miles on the assumed original plugs. when i first got my 06 it would average a calculated 48 or so mpg. as i closed in on the 26000+- miles the mpg dropped down to 43 or less. replaced the plugs with a set of iridium plugs...i'm now seeing 49 ... 50 mpg!

I think you and previous posts have covered the logical first steps. Plugs, filter, Seafoam.

The fuel gauges are not accurate. Manual calculation is needed.

City 40 Hwy 48 Combined 44 if I am driving like Miss Daisy.

I don't see what bike, ST1300 or ST1100?

Regardless, I agree with what's been said about checking spark plugs and air filter first.

Bike is st1300, and I ride very modestly. I will check back once I do the plugs.
I have a very silly question, how do I remove the plastic clips that hold the plastic on the bike? Also what else do I need besides new plugs, any seals or caps, etc?

Tupperware removal, see link: http://www.touringmotorcyclists.com/tech_tips/st_tech_tips/front_fairing_removal.html

Be sure to keep connectors separated by component removed, maybe labeled baggies. No left over parts.

any seals or caps, etc --- not to check plugs and air filter.

Note on plugs: NGK lists a cooler plug that the manual. Many here use it and it seems to work fine. I prefer to stay with recommended heat range.

Guttooth71 said:

When I start the bike up thermostat warms up like it should to three bars and stays at three bars. Original was already replaced, Maybe it's going bad but it's not acting like it.

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Low MPGs are a big indicator of a bat t-stat... however, the temps have to be in the 40's or maybe 50's when you are riding before you'll typically see the bars drop below 3 given a failed thermostat. I don't remember if you'll get low MPG's in summer riding w/failed thermostat, but I think that's true as well even though the forward movement and fan will keep the bike cool and probably on 3 bars.

Thank you very much!

I think I may replace thermostat when I do the plugs. It's fairly cheap and will narrow the issue down further. thanks for everyone's help, I assume I will be saving money since most placed charge 66-75 and hour for labor.

I average about 34-ish combined, using the odometer and fillup to compute. I live in a small town. At a stoplight I get "--" on the gas mileage indicator. Puttering around near work in 1st I get less than 10mpg on the indicator. On the country road home, I think of 5-50-50. If I'm in fifth gear at 50mph, I get ballpark 50mpg. A little less on the uphills and a little more on the downhills.

The 34 seems consistent with mine. The other posters will know more about the gas guage.
Noel

You don't need to remove hardly any plastic to get to the plugs. Just the small inspection piece near your knee and the silver plastic cover that goes over the plugs.

To take off the minimal plastic and change out the plugs should only take about a half an hour.

Sportznut said:

You don't need to remove hardly any plastic to get to the plugs. Just the small inspection piece near your knee and the silver plastic cover that goes over the plugs.

To take off the minimal plastic and change out the plugs should only take about a half an hour.

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You do have to be VERY careful doing it that way however - as you can break the boot on the ones further towards the rear - always best to wait until you have a reason to take the plastic off IMO.

Guttooth71 said:

Bike is st1300, and I ride very modestly. I will check back once I do the plugs.
I have a very silly question, how do I remove the plastic clips that hold the plastic on the bike? Also what else do I need besides new plugs, any seals or caps, etc?

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This doesn't answer your question, but the only plastic that needs to be removed to change the spark plugs is the small "inspection cover" on each side and the plastic head cover from each cylinder head. Changing spark plugs is child's play, takes about 30 minutes if you take your time. If I remember correctly, the owners manual tells how to remove/install the push pins that hold the inspection covers in place. All you need to do is push the center pin down with a small screwdriver or similar tool, then get a fingernail under the outer part of the push pin to lift it up.

Also, don't bother going to the trouble of replacing the thermostat unless you can confirm the one you have is bad. Replacing the T-stat is Not child's play, but nearly an all day job as the tupperware needs to be removed, as well as the radiator, to get to the T-stat.

I changed the plugs and cleaned the air filter. Still calculating 34mpg driving conservatively. Bike warms up quickly to three bars and stays there. Can it be a sensor? Or most likely the thermostat?

Also the gas gauge is broken , when I fill up it shows a bar below full, drops quickly and starts blinking with 2.8 gallons still in it, help!

What gear are you riding in, if not in top (5th) then your mileage will suffer.

Guttooth71 said:

164 miles then I filled up with 4.8 gallons of fuel. Gauge had two bars left. I filled up and drove 8 miles and two bars are already off full tank.

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Filled on side stand or center stand? That could be part of the gauge response. The two gas tanks add up to 7.6 gallon. The upper has the gage float, the lower gas tank has the thermistor that just knows wet or not wet with gas. 7.2 gallons used is VERY close to pushing the bike.

Poconos have lots of twists and hills which are gonna put a dent in mileage.
If you still get 45ish mornings up there you can take it out on the hiway and see if you can get the coolant temp to drop to 2 bars. If so, you have a mileage eating stuck open thermostat.

42psi front and rear.

The rear brake disk should be warm not hot after a casual ride. If it's hot it could be a sticky SMC applying some rear brake.

A new air filter is always an easy thing. Emgo makes an OEM style that costs less than the honda.
Tip- leave the front two screws in the air box cover surround after you back them out. They're easy to drop where that can't be easily retrieved.

+1 on being careful trying to pull plug boots without damaging them. Best to pull the plastic.

The silver covers have grommets that push on posts and two fingers that slide into channels on the bike so it's a two step removal process.

1- push in the center of the plastic rivet that holds the fairing cover access cover then pry the hole thing out. Reset the pin to above flush for reinstallation then push flush to engage it. Swing the cover out then remove it.

2- put your fingers in the rear opening of the silver cover that says honda and pull up firmly to release the grommets. Then slide the cover forward to release the two fingers. (the right side is also the oil fill port access).

Check the article section for the tupperware removal cheat sheet that lists all the different plastic rivets and and bolts that hold the fairings on. It's a help for you 1st full fairing removal process.

Guttooth71 said:

Bike warms up quickly to three bars and stays there. Can it be a sensor? Or most likely the thermostat?

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These bikes don't have a record of sensor failures, but early ones like your '03 are almost guaranteed to have their thermostats fail. The working theory has been that paint overspray around the radiator fittings gets broken up by the hot coolant, circulated and ends up getting the thermostat gummed up and stuck partially open. You won't see anything on the temperature gauge that shows it until it's cold outside, but even in warm weather it will have some effect on your fuel economy.

The kind of riding are you doing also has a pretty big bearing on it as well. It's very easy for me to get 36 MPG around town, because the 1300 eats fuel at idle. The first leg of my trip home this weekend was all open road at about 60 MPH and I was getting 47+ MPG.

Also the gas gauge is broken , when I fill up it shows a bar below full, drops quickly and starts blinking with 2.8 gallons still in it, help!

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If the entire display blinks, that means the dash has lost contact with one of the fuel senders (there's one in each tank). The one in the upper tank is known to fail; replacing it is easy.

--Mark