Gas cap wistling

[Mig21]

Hi

A few times now, after riding the bike for more than 30 minutes, I've heard some strange wistling noise coming from it, even with the ignition off.

Sounds like air escaping through an imperfect rubber seal.

Today I noticed it again, and it lasted long enough that I'm pretty sure I know where it comes from - the cas cap. I opened it and the whisling stopped, though I guess that could have been coincidental.

I did stick my finger in and the insides of the tank are definitely warmer than the environment, though I wouldn't call it hot.

Is this something bad? Is there something I should double-check?

The bike is a Vulcan 500.

Thanks in advance.

[RonnieRev]

The fuel tank has to vent, and my Kawasaki vents thought the gas cap, you may have a resriction in the cap assembly causing the wistle.

[frekeyguy]

does that bike have a fuel pump?

[Mig21]

does that bike have a fuel pump?

I guess not, I don't see a reference to it in the manual.

[Brian P]

I have never owned a Kawasaki that did NOT whistle from the gas cap when the temperature of the fuel tank changes. The temperature change can come from the engine heating up or cooling down, or from the sun shining or not. It is of no concern whatsoever and is normal.

[zacm7]

its normal my zx7 does it when the tank is full or its really hot. my old 1990 rz350 did it as well

[Mig21]

Thanks guys

[Mach12R]

Its commin on all ZX14's to.

[kneedragger88]

Gas expands when hot and contracts when cold displacing the air by volume in the tank. The cap vents the air.
Next time you fill up look at the pump. They are calibrated to dispence volume corrected to 15 C. Years ago when I was driving gas tankers the load would change up to 800L on a 65000L load when extremely warm or cold.

[Mig21]

Gas expands when hot and contracts when cold displacing the air by volume in the tank. The cap vents the air.
Next time you fill up look at the pump. They are calibrated to dispence volume corrected to 15 C. Years ago when I was driving gas tankers the load would change up to 800L on a 65000L load when extremely warm or cold.

Holy crap, is that not a typo? That's more than 80 times difference. What kind of temperatures are you talking about? Just plain old gasoline?

[tat2]

Holy crap, is that not a typo? That's more than 80 times difference. What kind of temperatures are you talking about? Just plain old gasoline?

Pretty sure he means the 65000L load would fluctuate 800L + or -

Not go from 800L to 65000L

[Mig21]

Oh, yeah - I didn't read it properly.