Bad Gas Mileage

freetime2247 said:
This morning I left for a 210mile round trip and temps where in the low 50's. Istill got three bars on the temp gage however, the miles per gallon on theinstrument cluster was showing a low of 28 and a high of 34 while cruising at70mph. Then on the return trip with temps in the high 60's the miles per gallonon the instrument cluster showed a low of 33 mpg and a high of 43mpg.
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That does sound very much like a thermostat sticking open. The mid 50s seems to be the point where the air temperature starts having a bigger effect on the cooling system.

freetime2247 said:
Very surprising that these bikes can go from 45mpg to 30mpg and no throw a fault code.
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The ECM can't watch for every possible failure in the engine because the sensors just aren't there and the bike would be a lot more expensive if it were. You'd have to keep track of a lot more variables over time to figure out that the engine isn't reaching the right temperature, and there may not be enough horsepower in the ECM to do that. If the engine doesn't maintain its temperature, the reaction is to burn more fuel, which turns into poor fuel economy, and that's your indication.

I wouldn't worry too much about actual MPG vs. what the dash says. Mine has been very consistently off by 3 MPG, and you've spotted the downward trend, which is the important part.

--Mark
 
Jfo, did you ever get your gas mileage back up to normal around 40 mpg or better? Sounds like you changed just about every thing including the T-stat. My current mileage is very similiar to yours.

I spoke with the dealer today and he thinks I have a vacuum leak somewhere on the bike. I'll keep you in the loop as they try to diagnose my issue.
 
No,issue is still unresolved..Hope your dealer has some good news .You don't have an aftermarket cruise control do you?
 
I am having the same issue. Bike runs great but its eating gas. I feel there is a leak but no signs of gas going anywhere. I have 48K miles and it is going to the dealer tomorrow to have the valves checked. I had 1 bar over 1/2 marker on the fuel gauge. Drove 120 miles and the last bar is flashing. At times my wife says she smells gas. I changed the air cleaner and checked the plugs. I think the valves are out and hope that fixes it. But after reading this I will have the dealer look further into issues raised here and let everyone know what I find out.
 
white courtesy phone's been ringing off the hook :call:
working on finding the cause....work in progress...jfoST is gonna try a couple things and let me know how it worked.
Will keep everyone posted of any possible fixes.
Igofar
 
My bike is still at the dealer and they have not started working on it yet however, I'll keep giving you guys a progress report as soon as I get some news.
 
Dang, I wished you guys lived closer to me.....my service would exceed your expectations, and save you alot of money for pie :D
 
I keep wondering if the cat convert's are plugged. If it was running bad at some poiont, the cats will melt down inside, causing abnormal backpressure. Don't know how to check this, or, for that matter, if it's even a viable possibility. Just thot I'd throw that out there, see what the feedback says.

Maybe you've wanted an excuse to change your exhaust? Here it is! lol
 
You'd think the ss cat shell would be blue (not the normal straw color) so I don't think so?
You could always pull it and see if you hear broken cat pcs rattling around in there when you shake it.
You could also compare how intake vacuum changes at idle and at maybe 2500 rpm.

Temp dependant mileage change like that sure could be a stuck t-stat. Might have to get down 45 or so to do the 3-2 bar dance?
 
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Your hearing the death breath of you t-stat! I'd start with replacing that then doing the TB Sync.
 
How are you riding? What kinds of roads are you riding on, what speeds, any hills, etc? I have averaged 38-40mpg ever since replacing the T-stat right after buying my bike used. It was in the mid to low 30s before I replaced it. We have hills, and many 55+mph roads. On the highway at 70mph I average around 36-38mpg. If I ride back country roads following my wife on her bike (riding gentle) I can see upper 40s.

Re: O2 sensors- if they are very bad they will throw a code, but they can be somewhat dirty (worn) and throw readings off some without throwing a code. The same can happen with a temp. sensor that is off some. The computer will think the engine is too cold and enrichens the fuel mixture. This doesn't always throw a code, depending on how far off they are.

This is generically speaking, I can't tell you how sensitive the Honda system is.
 
I'm riding mine on flat terrain and at 70mph I’m getting around 30-33mpg. My bike has 70K miles and the T-stat has never been changed nor any electronics. New air filter, plugs, coolant change and valve check. Appears the temp sensor is accurate and I have noticed the bike gets a little better mileage at outside air temps above the 65F.
I have no indications of a bad T-stat judging by my temp gage. Comes up to 3 bars within a few minutes and stays there. Does take a little longer to get there in cooler temps (i.e. 55F and below). I'm thinking it could be oxygen sensor(s) but only time will tell. I can live with the poor mileage but sure seems to be a waste of money and gas not to be getting 40's for mileage.
 
until the temps are lower the bars won't go under 3 and bad mileage is the only indicator unless you remove the stat for checking.
 
freetime2247 said:
I'm riding mine on flat terrain and at 70mph I’m getting around 30-33mpg. ... Appears the temp sensor is accurate and I have noticed the bike gets a little better mileage at outside air temps above the 65F. ... I have no indications of a bad T-stat judging by my temp gage. Comes up to 3 bars within a few minutes and stays there. Does take a little longer to get there in cooler temps (i.e. 55F and below).
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This is all classic bad thermostat. Having thermostats stick open is a well-known, common problem with this bike that causes poor fuel economy even in warm weather and less than three bars in cold weather. Check yours before wasting time digging into anything else. If it isn't permanently stuck open, there's a procedure in the service manual for making sure it opens and closes at the right temperatures.

The coolant temperature gauge on the 1300 is controlled by the ECM, and it's pretty widely believed that it isn't linear, meaning that it gets up to three bars and stays there unless something way out of the ordinary happens. I can't get mine to four bars without disconnecting the fans and letting it idle for a good while and have only ever seen it dip below three when the thermostat was stuck open.

--Mark
 
Even when its in the 40's outside, I get the first bar around 1 minute, the second bar at two minutes, and the third bar by two minutes and 45 seconds!
This is another case of "I get all three bars after 15 minutes" type of thing. folks think just because they eventually get three bars that their T-stat is ok.
signs of it starting to die are, poor gas mileage, and taking longer than this to reach three bars.
Like Blrfl said, check your T-stat before digging in to anything else, I'll bet you'll be surprised. I can't count how many folks swore their T-stat was ok until I opened it up and showed it to them.
.02
 
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