Sudden gas mileage drop?

[HalfLiterBeater]

Ever since day one, this bike has unfailingly gone 180 or so miles before needing to be switched to the reserve tank. ALWAYS. Maybe a lowest of 170-175...hard city driving. Highway/steady speed driving would put it into the 190 mile range sometimes.

But the past two tankfuls now....I don't know..

The other day I was at 145 miles, when the bike displayed the characteristic signs of low gas. At first it just "didnt feel right", but I couldnt put my finger on it exactly. I was thinking 'feels like it's out of gas...but it's only at 145, it can't be!' Sure enough...wrapped the throttle, and the bike bogged down bad. I switched to the reserve...wrapped it a few more times, but it didn't get any better! I switched to the turn lane (lasted for miles on this road), pulled the clutch in, and the bike immediately shut off. Coasted it into the gas station by the grace of god...but not only did the entire tank empty itself, but somehow the reserve tank was emptied also, even though I had never kicked it to reserve. It took a good minute of cranking for it to fill up the fuel bowls enough to start.

Today, on the interstate...I was at 150 miles and it did the same thing! I had my reserve this time though----thank god, cause I was on the interstate in the middle of hickville, between exits...took me about 15 miles to find an exit with a gas station.


So my question is, why the hell am I suddenly hogging up gas? Bike only sat for about a week, maybe 2....that's it. Havent bought bad gas or anything like that....always decent 87 octane. Only got about 2500 miles on it right now. The fuel tank vent line seems ok...I haven't been riding with the choke on or anything dumb like that, and the choke isn't sticking either.

Any ideas? I'm going to pick up a can of some fuel additive and pour that in the tank....see if maybe there's some sh*t built up in the carbs or something, but really, I'm baffled. And irritated. :lame

[Jammin_Johnny]

Originally Posted by HalfLiterBeater

Ever since day one, this bike has unfailingly gone 180 or so miles before needing to be switched to the reserve tank. ALWAYS. Maybe a lowest of 170-175...hard city driving. Highway/steady speed driving would put it into the 190 mile range sometimes.

But the past two tankfuls now....I don't know..

The other day I was at 145 miles, when the bike displayed the characteristic signs of low gas. At first it just "didnt feel right", but I couldnt put my finger on it exactly. I was thinking 'feels like it's out of gas...but it's only at 145, it can't be!' Sure enough...wrapped the throttle, and the bike bogged down bad. I switched to the reserve...wrapped it a few more times, but it didn't get any better! I switched to the turn lane (lasted for miles on this road), pulled the clutch in, and the bike immediately shut off. Coasted it into the gas station by the grace of god...but not only did the entire tank empty itself, but somehow the reserve tank was emptied also, even though I had never kicked it to reserve. It took a good minute of cranking for it to fill up the fuel bowls enough to start.

Today, on the interstate...I was at 150 miles and it did the same thing! I had my reserve this time though----thank god, cause I was on the interstate in the middle of hickville, between exits...took me about 15 miles to find an exit with a gas station.


So my question is, why the hell am I suddenly hogging up gas? Bike only sat for about a week, maybe 2....that's it. Havent bought bad gas or anything like that....always decent 87 octane. Only got about 2500 miles on it right now. The fuel tank vent line seems ok...I haven't been riding with the choke on or anything dumb like that, and the choke isn't sticking either.

Any ideas? I'm going to pick up a can of some fuel additive and pour that in the tank....see if maybe there's some sh*t built up in the carbs or something, but really, I'm baffled. And irritated. :lame

Have you checked:

Air box & filter(s)?
Plugs?
Fuel filter?


Have you changed:

Gearing (bigger or smaller from OEM)?


Have you:

Drained the current fuel?


Some places to start.

[HalfLiterBeater]

Air box is intact, filter is clean.
Haven't checked plugs or fuel filter... I probably should....it's just I'm not used to checking things like this on a NEW vehicle!

The gearing hasn't been changed at all....
And it has done this on two tankfuls of gas from different stations, both 87 octane.

I bought some super-concentrated efi/carb fuel cleaner....it says it has jet fuel in it or something, as a carrier. So to avoid pinging, I topped the tank off with 89 octane. I didn't feel like pumping 93, and the tank was already filled with about 2.5 gallons of 87...so I figured why waste the cash for the 93. It's enough cleaner for 21 gallons of gas...I'm running half the bottle per tankful. I'm hoping to see some improvement, but...I doubt it.

[Topamax]

Is this your first bike? Or are your riding skills getting more aggresive than when you first got the bike? Sounds like you are riding harder now, than when you first got the bike. That would be my guess.

[MaxPower]

Have you checked for a fuel leak anywhere on the bike? It could be a slow drip.

How consistently do you fill your bike up with gas? If you fill it on the sidestand, you might be putting in less than if you fill it on the centerstand.

I agree that your riding style has gotten more aggressive, but I doubt it would cause such a sudden drop in mileage. Have you been riding at a higher speed on the highway, however?

Were this my bike, my next step would be to inspect the airbox and the carbs.

(I also hit about 180 on my EX500 before switching over to reserve in mixed city/highway riding.)

[HalfLiterBeater]

I am riding it more aggressively now...but I have been for the past month...and I still got the same amount of mileage out of it.

I do fill it on the sidestand...but I fill it right up til it gets to the filler neck, and stop. It usually takes something like 4-4.5 gallons that way when it's empty.

For the second trip that my mileage sucked, yes I was on a highway blaster. Average speed of about 90 mph, with stints up to 95. Rpms were around 7,000-7,500 steady. Would this make the bike hog down gas much faster?

[MaxPower]

Drag increases with the square of velocity at highway speeds. So increasing your average speed from 75mph to 90mph could lead to about a 40% decrease in mileage in theory.

Try driving with economy as your first priority on your next tank and see if that makes any difference. Sorry I can't help you with exact numbers any better.

[SportyChick]

Same thing happened to me on my F4i, I wasn't getting the same amount of miles on a tank that I was used to. Bike wasn't running right either, when accelerating, it would sometimes stutter and then catch.

I had taken the bike completely apart and exchanged fuel tanks. When I was putting the fuel tank on, I must have pinched the fuel line somehow cause when I unscrewed the tank and lifted it slightly, I could see the fuel line was crimped. Check your fuel line and make sure it's not crimped or obstructed in any way.

[HalfLiterBeater]

Thanks guys....I'll check it out. Haven't been able to ride much lately due to work, and the freakish FL weather. We'll see what happens though.

[MaxPower]

Keep us posted.

[tt600khatf]

Might want to make sure the carbs are in sync. Bad fuel mileage is a sign for unsynced carbs.

Keith

[HalfLiterBeater]

Carbs were synched at 600 mile service....Bike has around 2500 miles right now. 2000 miles shouldnt be enough to unsynch the carbs.....unless this bike REALLY sucks. ;)
Still havent had a chance to ride it you guys... I'm working 7 days in a row right now....so I haven't had the time for a trip. I'm taking it to work though...which is 20 miles each way. I'll let you know if there's any mileage change.

[stoinkythepig]

The bike has a vacuum operated petcock if memory serves. Might be a problem with it. I'd check it out for proper operation.