Gas Boiling?

Ross40 · Feb 18, 2017

Just got back from a little jaunt.. ambient temperature of about 60 F. Went back
Out to my bike and there was a hissing noise, the fuel tank vent. You could clearly hear it bubbling inside the tank. I opened the cap to let off the rest of the pressure thinking that would solve everything, it has still been bubbling for ten minutes with the tank cap open.

Any ever experience this or hear of it?

I did get stuck at a light and ran engine temp up to 219F (nothing wrong with that)

I was also pretty hard on the throttle up the long driveway before shutting off(maybe has something to do with it)

carlito · Feb 18, 2017

yeah I had the same thing happen last weekend. i could smell gas coming from the garage and when I opened the door I heard the hissing sound. It was seeping out from the vent. took the cap off for a few seconds and put it back on and it went right back to hissing. this was 10-15min after i had gotten home from a long ride. same temp... about 60 outside.

I am going to take the tank off tomorrow and make sure i dont have any kinks in the line. other than that i am clueless.

tadashi · Feb 18, 2017

I have the bottom of my air box, tank and fuel pump heat shielded. Needa keep the fuel cool

Ross40 · Feb 18, 2017

I have never noticed it before and I have ridden it much warmer weather. I'm wondering if the fuel I filled up during the ride played a part

Grinder · Feb 19, 2017

Might have a pinched vent breather tube under the tank

Ross40 · Feb 19, 2017

I'll probably be going on another ride today. I'll report back and take a video if it happens. Thanks for responses

Macattack · Feb 19, 2017

water boils at 212˚f but It might start bubble as low as 160-180
gasoline boils at 180ish˚ so it might start to bubble at 140˚

the fuel in your bike might also have started out lower temp so more condensed and Gasoline expands and contracts significantly with temperature changes; far more than water.

as counterintuitive as this may sound You are far more likely to experience hissing and expansion noises when your bike has been sitting on really cold nights and you fire it up for a jaunt on a mildly cooler day. In other words your fuel would be used to the delta of temperature you'd get in july , but the extreme difference you're experiencing in temperature from cold to almost warm is the reason for the noise .

theoretically you could start your bike with a full tank after a cold night . let it get to maximum engine temperature by idling it . shut it off let it heat soak and end up with 4% - 6%increase in volume depending on original fuel temp.

gas stations fuel is underground so the temperature is far more consistent .

I would doubt the fuel was boiling- It is plausible it was bubbling due to pressure and heat , but I doubt it until i see it.

Gas Boiling?

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