Hum Coming From Gas Tank Area

[le_penseur_imp]

Hi All,

Just received my 2017 EX yesterday. Will post some pics soon.

I noticed there's a periodic hum sound coming from the gas tank after shutting off the bike. Is this normal? I searched the forum and didn't see anything about it. It's sounds like a little pump or electric motor. I'm guessing it's the EVAP system, but I think it's been humming periodically all night since yesterday so why would it still be happening?

Thanks, any help is appreciated.

 

[LakeWylieJoe_imp]

That's a new one. Are you certain there isn't an insect caught up in there somewhere?

One way to eliminate that possibility is removing the negative battery cable while the sound is present. If the noise continues, it has to be a critter.

Let us know what you find!

Hi All,

Just received my 2017 EX yesterday. Will post some pics soon.

I noticed there's a periodic hum sound coming from the gas tank after shutting off the bike. Is this normal? I searched the forum and didn't see anything about it. It's sounds like a little pump or electric motor. I'm guessing it's the EVAP system, but I think it's been humming periodically all night since yesterday so why would it still be happening?

Thanks, any help is appreciated.

 

[le_penseur_imp]

Indeed haha! It is definitely not an insect, but I just went back to bike and it's not doing it now. I was looking at the service manual and it looks like the EVAP system has a solenoid. My guess is it's opening and closing the valves. The bike hadn't been started in awhile and just got to me in CA from FL so the gas may be going bad as well.

I will run a new tank through it and report back.

That's a new one. Are you certain there isn't an insect caught up in there somewhere?

One way to eliminate that possibility is removing the negative battery cable while the sound is present. If the noise continues, it has to be a critter.

Let us know what you find!

Hi All,

Just received my 2017 EX yesterday. Will post some pics soon.

I noticed there's a periodic hum sound coming from the gas tank after shutting off the bike. Is this normal? I searched the forum and didn't see anything about it. It's sounds like a little pump or electric motor. I'm guessing it's the EVAP system, but I think it's been humming periodically all night since yesterday so why would it still be happening?

Thanks, any help is appreciated.

 

[pekingduck]

There's nothing electrical that would or should be making the noise. I would take the seat off, pull the rear tank mounting bolt out, and check for a kink in the small hose that vents the gas tank.
Pressure built up inside the tank from heating and cooling should be going out through the hose to the evaporative emissions canister. The canister is charcoal filled, traps the vapors.
If somehow, the tank was overfilled well above the bar, fuel may saturate the canister to the point of clogging it. Open the gas cap to see if you hear a pressure release or a vacuum sound.

The other possibility is that the fuel pressure in the lines could be bleeding out through a sticking injector, or through the fuel pump's bypass valve. If you happen to be around when it's making the noise, open the gas cap to see if it gets louder. The evap solenoid only activates when the engine is running.

The line should hold 50psi for at least a couple hours, or maybe all night. When you cycle the key on, note how long it takes to build pressure back up compared to when you have just shut the key off, then back on.

 

[GoldOxide_imp]

I will buy the charcoal canister evap system suggestion.

My ol' Aprilia did it all the time, even 30 to 60 minutes after a ride. It would sound like a loan calf moaning in the distance.

There were no electrical interventions. The process was passive.

This is particularly most often in warmer weather riding seasons.

 

[Cormanus]

Hi All,

Just received my 2017 EX yesterday. Will post some pics soon.

I noticed there's a periodic hum sound coming from the gas tank after shutting off the bike. Is this normal? I searched the forum and didn't see anything about it. It's sounds like a little pump or electric motor. I'm guessing it's the EVAP system, but I think it's been humming periodically all night since yesterday so why would it still be happening?

Thanks, any help is appreciated.

It’s happy? :banana:

 

[le_penseur_imp]

Update, the sound immediately stops when I open the tank cap, but there is no pressure release occurring.

 

[Jfro5687_imp]

Hi there, the CB makes a lot of strange noise when it’s off and cooling down (in the garage post ride out). Often hours later I could be in the garage completely quiet when the bike would just start making funny noises for a few seconds or more then fall silent again. Almost like a haunting gurgling noise that is very difficult to describe. I wouldn’t say it was humming but I think this might be what you mean and is nothing to worry about. It’s the modern gummings evap system doing its thing. That’s all.

 

[Mixagon_imp]

Update, the sound immediately stops when I open the tank cap, but there is no pressure release occurring.

Mine does the same, I've stopped trying to find out why now because it does not seem to be doing any harm or affect the bike in any way.

 

[le_penseur_imp]

Glad mine is not the only one! I think they're just hibernating, getting ready for the next ride lol.

 

[GoldOxide_imp]

You can always remove the charcoal canister and properly terminate the hoses, however, that will likely invalidate the pollution certification for your jurisdiction.

 

[ampm7_imp]

My Moto Guzzi Eldorado (recent version) did the same thing. It sounded like whale moans. Open the tank cap and it goes away.

 

[pekingduck]

If you do disconnect the charcoal canister (not recommended), the vent line from the tank has to be left open. I've seen tanks that have imploded when capped off. That happens mostly when the tank is dark and sitting in the hot sun, and have imploded as it cooled off. Very rarely have I heard of one expanding, bulging out, curling the sides upward.

 

[Houtman_imp]

BIG stainless steel wine tanks can implode when they start bottling without having the top open to let air into the tank , I talk about tanks large enough to hold thousands of gallons .

 

[GoldOxide_imp]

If you do disconnect the charcoal canister (not recommended), the vent line from the tank has to be left open. I've seen tanks that have imploded when capped off. That happens mostly when the tank is dark and sitting in the hot sun, and have imploded as it cooled off. Very rarely have I heard of one expanding, bulging out, curling the sides upward.

This is not a big deal, and one has to do it right. A line is extended and left open, the other plugged. Bikes without "the can" have existed since the invention of the automobile. The point of the can is to help prolong [hopefully] a cleaner atmosphere longer for all to enjoy.

Here was my charcoal canister removed off my Aprilia. It was mounted on the side of the engine. Aprilia probably hastened that design as an afterthought to meet emission standards ...

 

[pekingduck]

To be clear, if the tank vent line from the fuel tank to the canister is removed at the canister, it must remain open, not blocked or plugged.

 

[Ninemeister_imp]

Just to clarify what others have said:

Inside the fuel tank is the fuel pump.
Whilst it often primes the fuel line/rail and injectors prior to start it never runs when the engine is shut off.
The fuel pump is fitted with a non-return valve.
The fuel rail remains pressurized when the engine is shut off, the pressure retained by the fuel pump and fuel pressure regulator.
The rail maintains pressure to aid warm start by preventing the heat of the engine from vaporizing the fuel and causing a vapor lock.

The active carbon filter is there to scrub hydrocarbons from and gasses that are vented to and from the fuel tank.
The engine management system controls a solenoid valve which connects the canister to the intake system.
When the engine is off, the valve closes to prevent fumes from building up in the intake manifold (which could cause a backfire on start up).

The noise you hear could either be pressure releasing (unlikely) or a vacuum drawing air into the gas tank following a drive.
Air going in is fine and likely to be a vacuum bleed designed into the system.

Hope this helps.

 

[Tev62]

Is the charcoal canister just a CA requirement or do all US bikes have it? These are not fitted to the European spec. bikes.

 

[pekingduck]

Is the charcoal canister just a CA requirement or do all US bikes have it? These are not fitted to the European spec. bikes.

Charcoal cannisters are required for California bikes, but since the CB1100 was a relatively low volume model, only California models were imported to the US. Saves $ on certification, logistics, etc.

 

[Mixagon_imp]

Is the charcoal canister just a CA requirement or do all US bikes have it? These are not fitted to the European spec. bikes.

So if my European bike does not have a charcoal canister that rules out the noise from being the canister.