Fuel Vent

[ahh-cool]

My MPG is horrible, to the point that I think I'm losing fuel through the vent line. I re-routed the line as high as I could in the engine compartment and then back down through the hole it was in originally.
I left it long and tied it back temporarily. I ordered a check valve for the vent line.
After my ride on Saturday, the tank was almost empty and the vent line was leaking fuel.
I have since installed the check valve and will try that when I ride again
I'm getting on average of 22-23 MPG.

 

[Bob Denman]

Have you had your dealer take a look at the purge valve? :dontknow:

 

[bruiser]

Hopefully that check valve will not cause any back pressure in the canister. Agree with Bob. Need to have the purge valve looked at. By the way, when gas vapors condense they turn to liquid.

 

[Rd_Runner]

Any other symptoms???

My MPG is horrible, to the point that I think I'm losing fuel through the vent line. I re-routed the line as high as I could in the engine compartment and then back down through the hole it was in originally.
I left it long and tied it back temporarily. I ordered a check valve for the vent line.
After my ride on Saturday, the tank was almost empty and the vent line was leaking fuel. View attachment 96523
I have since installed the check valve and will try that when I ride againView attachment 96524
I'm getting on average of 22-23 MPG.

Does your bike sputter any? I would check the two vacuum lines to the MAP sensor. They are known to crack on the Spyders. When that happens the computer is going to increase the fuel output to compensate for the vacuum leak, resulting in increased fuel consumption.

- Mike

 

[Magdave]

My MPG is horrible, to the point that I think I'm losing fuel through the vent line. I re-routed the line as high as I could in the engine compartment and then back down through the hole it was in originally.
I left it long and tied it back temporarily. I ordered a check valve for the vent line.
After my ride on Saturday, the tank was almost empty and the vent line was leaking fuel. View attachment 96523
I have since installed the check valve and will try that when I ride againView attachment 96524
I'm getting on average of 22-23 MPG.

It is normal for the V twin. Not right but normal to get some drips from time to time as said above the fumes condense in the line. You obviously are boiling fuel like most of us do. Your MPG may be because of your riding style. I average between 25-26mpg and keep the RPMs near 5k. On longer runs with no stop and go I get a couple more mpg. I accelerate slowly no faster than the cars around me from a stop. The check valve will do nothing but possibly do damage depending on which way you have it installed it will either do nothing or blow the hoses off :yikes: I would remove it ASAP.

 

[jaherbst]

Boiling fuel in the tank will evaporate some of your fuel and will contribute to poor mileage.

 

[jcthorne]

My MPG is horrible, to the point that I think I'm losing fuel through the vent line. I re-routed the line as high as I could in the engine compartment and then back down through the hole it was in originally.
I left it long and tied it back temporarily. I ordered a check valve for the vent line.
After my ride on Saturday, the tank was almost empty and the vent line was leaking fuel. View attachment 96523
I have since installed the check valve and will try that when I ride againView attachment 96524
I'm getting on average of 22-23 MPG.

That check valve is a VERY BAD IDEA. There is now no where for the fuel vapors to escape. The tank, fuel lines etc will all get pressurized until the weakest link is found.....

The poor fuel economy is likely do to the fuel vapors exiting out that hose. The fuel boils due to excessive heat in the engine bay and vaporizes. The drips you see are from the vapors recondesning in the vent line before they exit. The whole fuel vapor venting problem is a design flaw. One the NHTSA is already looking into. You should add your complaint to the file.

 

[Bob Denman]

Stefan,
A lot of folks with "998s", have had their fuel tanks and exhaust systems wrapped...
Have you considered this course of action yet? :dontknow:

 

[Dragonrider]

I used a fuel filter with an "S" curve in the line. The filter allowed me to see what was coming down that line, and how much, without plugging it.

My milage on my 2010 was similar, until I did the CAT delete, added the Yosh exhaust, and switched to non-ethanol fuel. Then I got it up to the mid 30s - but it took all of that to do the job.

 

[ahh-cool]

Does your bike sputter any? I would check the two vacuum lines to the MAP sensor. They are known to crack on the Spyders. When that happens the computer is going to increase the fuel output to compensate for the vacuum leak, resulting in increased fuel consumption.

- Mike

No, but I will check tomorrow

 

[ahh-cool]

Stefan,
A lot of folks with "998s", have had their fuel tanks and exhaust systems wrapped...
Have you considered this course of action yet? :dontknow:

I put radiant barrier on the tank. Christmas time I plan on removing the cat and possibly wrapping the exhaust or ceramic coat the exhaust.

 

[ahh-cool]

That check valve is a VERY BAD IDEA. There is now no where for the fuel vapors to escape. The tank, fuel lines etc will all get pressurized until the weakest link is found.....
.

I'm not sure about that, I thought the fuel cap had a relief built in

 

[ahh-cool]

Have you had your dealer take a look at the purge valve? :dontknow:

I figured it's working since fuel is coming out

 

[ahh-cool]

This might be the problem for my MPG. I'm trying to slow it down

 

[ahh-cool]

I've been working on the bike and haven't had a chance to ride it till last night.
My tank was very low, I went to fill it and when I removed the cap I noticed it was slightly pressurized.
When I filled the tank, now that's where it was strange, you know how when you fill the tank and you keep adding fuel because it shows full and then the level drops down.
After the the pump shut off and I went to top it off again I overfilled the tank, that never happened before.
I will keep an eye on the pressurization and see what happens
Stefan

 

[ahh-cool]

I removed the check valve. My tank was pressurizing and you could hear the tank oil caning when I removed the cap.

 

[Dan_Ashley]

I like boiling fuel. It makes yummy frankfurters.

 

[Dragonrider]

Yours, not mine.... frankfurters that is....