Flash boil in tank

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erniebearskin

Joined
Jun 26, 2011
Messages
24
Location
In the woods around Calgary Canada
After two hours of hard riding in mountains we stopped on top of hill for a breather. I was frustrated as my idle started creeping up and up while stopped and wanted to see if I could adjust. Upon stopping I noticed my vent was whistling so I was curious if I was building excessive pressure in my tank, so I turned my fuel cap, and it popped off with all the pressure, upon decompression the fuel instantly starting boiling so rapidly it started bubbling out of the tank. After uncleanching my butt cheeks I quickly slammed the cap back on.

Scary stuff. 2011 FE390 with billet cap and the stubby vent from Hardparts catalouge.

Im assuming vent was not functioning correctly and the pressure in tank not only was causing the bike to overfuel and idle to increase, but pressure was also raising the boiling point of the fuel.

Anyone else experience this?
 
I can't hardly use the stubby little vent cap. Last time I went riding on my 2011 FE-570, I took off my little blue vent cap on my stock gas cap and couldn't believe how much pressure was in there. Shortly thereafter, the bike quit running and hasn't started since. Fuel pump is pressuring up, I have spark, but it won;t start or run.

I am about done with this bike.....
 
You need to get rid of the stubby vent and go back to this setup:
Fuel+Tank+Breather.JPG


That stubby vent has a one way valve in it that does not let the tank breath as the fuel gets heated up.
I had the same problem.

More info in this post:
Fuel cap vent
 
If you take your tank cap off and rattle it, you'll hear the little valve inside it work. If you do the same with the stubby vent independent of the tank cap, you will hear the same thing. Those two valves do not apparently work together well. If you're going to use the stubby vent, take the tank cap apart and defeat the valve inside it. If you want to leave the tank cap alone, then ditch the stubby vent. I did the former - I got rid of the stubby vent and used clear fuel line on the tank cap so that I could see what was going on. Clear hose gives you a visual that rubber hose won't give you.
 
Ruger said:
If you take your tank cap off and rattle it, you'll hear the little valve inside it work.
Click to expand...
The Valve in the Billet Tank Cap only stops fuel coming out if the bike is upside down. It does nothing when the bike is right way up!

Ruger said:
If you do the same with the stubby vent independent of the tank cap, you will hear the same thing. Those two valves do not apparently work together well. If you're going to use the stubby vent, take the tank cap apart and defeat the valve inside it. If you want to leave the tank cap alone, then ditch the stubby vent. I did the former - I got rid of the stubby vent and used clear fuel line on the tank cap so that I could see what was going on. Clear hose gives you a visual that rubber hose won't give you.
Click to expand...

I got rid of the stubby vent as I could not work out how to get it apart to remove the one way valve. Even if I did get the stubby valve apart to remove the one way valve, I figured it would spew petrol straight out that vent when the tank was full and heating up due to slow riding.
 
There was a recent post here in which a poster was advised by a dealer (I think) that the valves in the cap and stubby vent were incompatible. The poster took the cap apart, removed the valve parts, and evidently solved his problem.
 
Ruger said:
There was a recent post here in which a poster was advised by a dealer (I think) that the valves in the cap and stubby vent were incompatible. The poster took the cap apart, removed the valve parts, and evidently solved his problem.
Click to expand...

Just because he is a dealer doesn't mean everything he says is correct. You get people who talk complete **** in any business, so the bike business is no different.
If you read lots of posts on here you will notice there are even special people on UHE too :crazy:
Even KTM have Looneys working for them in the factory, take a look at the factory Map Switch, the guy that designed that clearly had a few roos loose in the top paddock :confused2:

The valve in the Billet Fuel Tank Cap and the valve in the Stubby Vent work in the same direction. They both let Air into the tank, but they don't let Air or Fuel out. The only difference is the Billet Fuel Tank Cap valve only works when the bike is on its side or upside down. The little valve mechanism inside the Billet Fuel Tank Cap is sufficiently heavy enough to stay open when air needs to get in or out of the tank while the bike is upright.

I have never had the boiling fuel issue until I ran the Stubby Vent. The build up of pressure was unbelievable.
 
Davo,
Do you think that the doubled function of the two valves is what created your boiling fuel problem, or just that the stubby vent is a bad idea on Husabergs?
Russ
 
Well, I went for a short ride today. It's hot out - aobut 90. On the street riding back home I looked down at the clear fuel line I've got on the top of the fuel cap, and there was a small amount of fuel in the line and it was bubbling furiously. I ditched the stubby vent and the valve in the factory cap is apparently doing its job. So the fuel in the tank is getting hot from either the engine or the exhaust mid-pipe because it passes so close to the tank. Which do you think is the primary source of the excessive heat - the engine or the exhaust??? This is a 2011 FE570S.
 
I put a CV4 blanket on my 2011 570S and it made a big difference in the fuel temp. Before my camshaft crapped out, I noticed a significant difference in the pressure on my fuel tank.
 
Electrified, do you have any photos of what you did?
And what is a CV4 blanket?
 
I have the billet gas cap and stubby blue vent on the gas cap and I have "not" noticed any problems?

Should I ditch the stubby vent or what? My fuel sometimes looks like it's boiling because I see fumes coming out from tank when I open the gas cap.
 
maKe, I didn't know I had a problem with hot gasoline (think about that) until I took off the stubby vent thing and replaced it with clear fuel line. Being able to SEE what's going on is very illuminating!
 
A CV4 blanket is a heat reflective "blanket" that attaches the the engine side of your gas tank. I believe you can accomplish the same thing with heat reflective tape but I liked the concept of the blanket better.
http://www.cvproducts.com/Powersports/

I can't post a picture because my bike is in the shop again getting the camshaft replaced under warranty. It has been there for 3 weeks so far with no end in sight. :angry:
 
I had a stubby vent of another brand, together with a nice vent.

Guess what? On the dynobench we found a magic dip around 8.500 rpms. No explanation.

We were stunned. Tried everything. After 4 runs the engineer got a bright idea and removed the stubby vent.The dip in the power was gone. This was on an RMZ450, fuel injected.

I can imagine these bling items cause problems to our Burgs as well: get rid of them :cheers:
 
Well I wanted to get my hands dirty in the garage, and had a nice supply of installation beer so heres my conclusion.

I took the stubby blue bling bling vent off from the billet gas cap and tested how it works. I could suck air in but not blow out, obviously the check valve inside it prevented to blow out. I tested the gas cap and I could suck in and blow out!

So in the current condinition my bike would vent normally air in the tank so fuel supply would work, but if there was pressure in the tank it could not escape anywhere.

What I did was really a simple fix. Put the stubby blue vent thing on vice, then used vice grips and pulled it apart so I was left with the blue cap and the hose fitting that keeps the check valve ball in it. Put then the hose fitting on vice and used vice grips to pull it apart again to reveal it completely. Took out the small bearing ball that was inside it, and assembled to whole thing back.

Now it works both ways and I can either suck or blow air through it. :cheers:
 
You stubby vent now functions like a piece of open hose. You might as well just run a clear length of fuel line from the cap to the steering head as I did. At least that way you will get visual feedback as to what's going on with your fuel.
 
Ya I know. But I like teh bling so now I can basically keep the current vent. :D

Also removed the check valve from gas cap. Don't know yet was that good idea, but at least it's not going to get stuck or anything anymore.
 
maKe said:
Ya I know. But I like teh bling so now I can basically keep the current vent. :D

Also removed the check valve from gas cap. Don't know yet was that good idea, but at least it's not going to get stuck or anything anymore.
Click to expand...

Bad idea removing the check valve in the Billet Gas Cap.
The valve in the Billet Fuel Tank Cap and the valve in the Stubby Vent work in the same direction. They both let Air into the tank, but they don't let Air or Fuel out. The only difference is the Billet Fuel Tank Cap valve only works when the bike is on its side or upside down. The little valve mechanism inside the Billet Fuel Tank Cap is sufficiently heavy enough to stay open when air needs to get in or out of the tank while the bike is upright.
 

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