I have a 2007 FLHTCU and was getting an average fuel mileage of 42 to 45 mpg before October of 2008. While in the smokies my fuel mileage was outstanding averaging 48 mpg, but on my return trip, an while traveling through Fort Payne, Alabama along the interstate, I noticed that my fuel mileage had fell off dramatically!!!

I usually get about 200+ miles per tank, and 100+ when at a 1/2 tank, well while traveling through Fort Payne I noticed I was just below a 1/2 of a tank and I had only traveled 62 miles since my last fuel stop. I first figured my fuel gauge had went on the blink, but at 115 miles my fuel light came on and I figured it might be a good idea to be on the safe side so I pulled off for fuel and to my surprise I had a little over a 1/2 of a gallon left in my tank before it was completely empty, yes it took me 4 1/2 gallons to fill my tank!!! and I only have a 5 gallon tank!!!

For the rest of the trip I monitored my fuel extremely close an determined I was only averaging about 30 mpg rather than my usual 42 to 45 mpg, depending on my riding habits.

After arriving home I began taking my bike to my local dealer hoping for a quick fix!!! well it's back in the shop again today for the 5th time an still my fuel mileage is terrible!!! They have changed the SERT program several times and with the last change I was getting between 33 and 35 mpg.

The dealers either giving me the run around or they are truly stumped!!! Either way, I have to get my bike back and running like it use too. The dealer admits the low fuel mileage is a problem, but they state they have no idea whats wrong!!! I am posting this thread and hoping that some of you guy's have an answer or have had a similar problem with a fix.

Thanks again for taking the time to read my post and if you have any suggestions or fixes please post them or PM them to me!!!

"D"

 

Wow what a dramatic change. I'd be upset too.

How often do you ride? Have you been riding continuously since October and the change was just sudden and permanent (versus the bike was in storage for a couple months)? My point is if it sat for a period maybe you've got a restriction someplace (air cleaner or mufflers from a mouse, or a kid shoved a banana in your tailpipe, etc).

I know when on a road trip I noticed a fairly noticable difference in MPG's in different states and all I could attribute it to was the fuel blend. It went back to normal after I left those two states I'd been passing through (WA and ID). I assume when you got home from your trip that the mileage did not return to normal.

I'll be watching this post as I'm a bit stumped too...

 

I'm sure you've thought of this already, but, did you check for any leaks? With your milage dropping while you are rideing, makes me think more of a leak.

 

What do the plugs look like?

 

Been riding on an off all winter. I live in Southeast Louisiana, so my weather through the winter months is pretty mild and the longest my bike has set has been for about 2 weeks or so, it'd be safe to say it's been rode considerably since returning from my trip... "D"

 

They look good, that was the first thing we changed and they've changed then again just to make sure the plugs weren't from a bad lot, if thats even possible... "D"

 

Try some autolite spark plugs, think its a 4164 plug. Ck yer air filter too. Try to use Exxon, Chevron and stay away from gas with Ethonol in it.
Check the air pressure in yer tires and look at the thread on them.
When did you change yer oil last.

 

Valve seat leaking? Did you have the dealer run a compression test?

 

Actually they're putting it on the "Rack" this time, according to the service manager to check and physically inspect the injectors to see if one of them is leaking. They said the only reason this hasn't been done before today, was because the "COMPUTER" said there was no leaks detected and all was good!!!

The only thing they did, to my knowledge besides re-mapping the SERT, was they said they reset the air to fuel ratio, because one was 103 an the other was 97, so both were reset to 100, but still no fix... "D"

 

Oil was changed and my bike thoroughly serviced just before my trip to the Smokies in October. Also had a new rear tire put on just before I left, The front tire was good at 70% when I changed the rear tire... "D"