The CB1100 Community Forum

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

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

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.

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 .

(06-27-2021, 04:07 AM)pekingduck_imp Wrote: [ -> ]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 ...

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.

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.

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

(06-28-2021, 06:37 AM)Tev62_imp Wrote: [ -> ]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.

(06-28-2021, 06:37 AM)Tev62_imp Wrote: [ -> ]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.