My GRiSO Is Squealing (High Pitch Squeal)

Well after 3 weeks of ownership, the new GRiSO has been great, except for one little issue. Maybe I can get some thoughts on this. After riding and shutting off the bike, it makes this high pitch squeal on and off ( every 10 to 15 seconds) for the next couple of hours while sitting in the garage or wherever its parked. Its not very loud, but it kind of sounds like when you slowly let air out of a balloon while pinching the air exit. I've tried to track it down, its definitely pressure built up in the fuel tank and the vent line going to the charcoal canister. The squeal seems to be coming from the little blue round thing on the right hand side thats located on the line that's going into the charcoal canister. this little round plastic blue thing kind of looks like a small fuel filter, I know its not but I'm not really sure what it is. My biggest concern is that if I'm getting a lot of tank pressure build up causing fuel tank expansion due to a lack of venting, it could possibly cause paint cracking. Has anyone experienced anything like this. I'm thinking maybe disconnecting this line from the charcoal canister to see it the canister may be the cause of air venting blockage. Anyone have any thoughts? Thanks from the new guy on the block.

Remove the canister. It does nothing for the bike and is just another potential air leak source.

Yup, the 'Little blue round thing' is a one way valve. These are commonplace and are supposed I believe to minimise hydrocarbon expulsion from the tank by dissuading, but not preventing, venting from the tank. It is also not unknown for them to be installed back to front or be of such crappy quality that they effectively seal the tank causing it to swell in hot weather when parked. This can be bad enough to have serious consequences, especially with machines with plastic tanks.

Some early Aprilia Manas had such awful non return valves that the tanks, (Which are under the seat and just above the rear wheel.) would swell to the point where they would rub on the rear tyre! There were several reported cases of the tanks actually being worn through by the tyre while the bike was being ridden. As you can imagine the results weren't good!

A common modification in the US, (We don't have the requirement for this tiresome accessory here.) is to remove the canister and its assorted plumbing and just allow the tank to vent to atmosphere as it does in most, if not all, of the rest of the world. While some people do report associated poor running with the charcoal canister system I have to say it made no difference to either my American GRiSO or my Mana GT in the US, at least not when I owned/rode them.

No doubt some members here can give you some easy instructions on the removal of both valve and canister. Just remember that you have to seal off the ports to the inlet manifolds after the canister is removed.

Sounds good to me. Didn't know if it would affect anything.
Thanks for the info.

I notice you live in Florida, and hot weather can cause lots of vapor to enter that catchment system. I'm guessing too that it's a check valve you're hearing as the bike cools and the pressure vents off into the canister. One caveat about removing the whole mess - if you keep the bike in a closed garage, gas vapors could stink up the space. Something you might try: when you pull up to your parking spot after a ride, pop the cap on the tank to neutralize pressure. If you get quite a "foosh" when you open the cap, the check valve may be sticking, and you might try replacing it. Shouldn't be too expensive, but I may be wrong...

Strangely, very small piglets are often attracted to Italian machinery.

Check, very carefully, inside your machine. If a visual inspection shows nothing untoward, remove the fuel tank and drop the engine and gearbox.

Most owners find that this movement will release the piglets. If it does not, you may have "gripper piglets" which will require a full engine strip.

Sorry if this is bad news. In general, parking your Moto Guzzi at least four feet in the air tends to discourage this kind of infestation.

Next: the perils of worms.

GNORTS wrote:

I notice you live in Florida, and hot weather can cause lots of vapor to enter that catchment system.  I'm guessing too that it's a check valve you're hearing as the bike cools and the pressure vents off into the canister.  One caveat about removing the whole mess - if you keep the bike in a closed garage, gas vapors could stink up the space.  Something you might try: when you pull up to your parking spot after a ride, pop the cap on the tank to neutralize pressure.  If you get quite a "foosh" when you open the cap, the check valve may be sticking, and you might try replacing it.  Shouldn't be too expensive, but I may be wrong...

Yeah I do get the pressure release when opening the fuel tank cap (big swoosh), and the heat in Florida definitely contributes to the fume expansion in the tank, it always has on some of my previous bikes. I figure its probably that little valve also since that's where the squealing seems to be coming from. I've reconsidered removing the canister, that most likely would give them grounds to void my warranty. Guess its going to have to go in and I'll have to let them check it out. I've priced the valve, Its $33.00.

Could I just remove the one way tip over valve and re-connect the two hoses with a barb fitting without any IL effect? This way if I ever have to have any warranty work done, I cold just put it back and they'd never know.

I yanked that crap off the second day I got the bike...I had it planned too.

It's a very common "affliction". My GRiSO has always done it, even with the charcoal canister removed. Every once in a while, if it bothers me, I just burp the tank by popping open the filler cap and it goes away.

Certainly nothing to worry about.