My Fuel Tank...whistles!

[CBXRider]

I may have mentioned this before. When it's hot outside vapor? is escaping thru the gas cap and whistles for a few seconds and then stops. Then it repeats all day. If I open the cap I hear a whoosh and the whistling stops. I've tried silicone spray on the gasket, cleaned the gasket and lubed it but still it whistles. I've raised the tank but haven't removed it but didn't see any reason why it would whistle. Am I going to have to remove it and locate and replace any and all vent hoses to cure this?

 

[djorgensen3]

Probably a pinched vent line is all it is....

 

[CBXRider]

Probably a pinched vent line is all it is....

But where? I can't see any pinched line.

 

[djorgensen3]

Just have to follow the tank vent line all the way down....

 

[Popie]

With the tank raised you can see the two hoses on the right side at the rear of the tank. The larger one is the drain hose. The smaller is the vent hose. Remove the vent hose and simply blow thru it. If the hose is clear you have a restriction on the tube it goes on within the tank. If you can't blow thru the tube it's restricted and either needs to be cleared or replaced. This has nothing to do with gas cap.

 

[dadofthree]

Check the vent

 

[Popie]

With the tank raised you can see the two hoses on the right side at the rear of the tank. The larger one is the drain hose. The smaller is the vent hose. Remove the vent hose and simply blow thru it. If the hose is clear you have a restriction in the tube that goes into the tank. If you can't blow thru the tube it needs to be cleared. This has nothing to do with gas cap.

 

[Popie]

OK... I guess I can fix your problem. But have no clue how to post here or go back and edit something I posted... My second post has the correct action to take if the tube is restricted.

 

[mjl3truck]

When you pop the cap open you'll find a rubber washer/o-ring that seals the cap to the tank. It also allows incoming air into the tank so it'll vent through the fuel cap.
You can remove that o-ring and it will vent better. I'm guessing that your vent mechanism in the cap is not functioning properly (rainwater and Bonneville killed mine). I found this out the hard way chasing a high rpm stumble at the Mojave Magnum using MR12. It would actually starve a little for fuel under high load/rpm. Pulled the rubber out all good. If you wanted to stay on the EPA's good side you could replace the cap. I guess this happens to Buells all the time too.

 

[CBXRider]

I know the rubber gasket is on the cap but are saying there is also an O ring?

 

[CBXRider]

If I have to clear the tube going into the tank, how? What crud am I clearing and don't want to push back inside? Or is it just residue built up on the inside of the tube? Pipe cleaners?

 

[notright]

It's usually just pinched somewhere. I had a custom that would starve out intermittently, Lots of head scratching later just a pinched equalizer line between the two tanks. Have you recently had the air filter out or the tank up?

 

[CBXRider]

It's usually just pinched somewhere. I had a custom that would starve out intermittently, Lots of head scratching later just a pinched equalizer line between the two tanks. Have you recently had the air filter out or the tank up?

No and no. No pinches either. Doesn't affect the running of the motor, just on warm days while sitting, it whistles and then stops and then whistles and stops etc etc.

 

[Popie]

No and no. No pinches either. Doesn't affect the running of the motor, just on warm days while sitting, it whistles and then stops and then whistles and stops etc etc.

This has nothing to do with your gas cap. And will not effect the way the bike runs. Your Breather Tube is clogged or restricted. When the temperature of the fuel increases it expands. The breather hose allows vapor to escape from the tank. Even if you do not see a pinch in the breather hose it can still be restricted. As I said before. Simply remove the hose from the tank and blow thru the hose. If the hose is clear the tube that it goes on is restricted. Either can probably be cleared by blowing thru them with compressed air. There is nothing else that can cause this problem. That's why they call this hose the Breather Hose. It lets the pressure in the tank remain equal to the pressure outside the tank at all times.

 

[notright]

This has nothing to do with your gas cap. And will not effect the way the bike runs. Your Breather Tube is clogged or restricted. When the temperature of the fuel increases it expands. The breather hose allows vapor to escape from the tank. Even if you do not see a pinch in the breather hose it can still be restricted. As I said before. Simply remove the hose from the tank and blow thru the hose. If the hose is clear the tube that it goes on is restricted. Either can probably be cleared by blowing thru them with compressed air. There is nothing else that can cause this problem. That's why they call this hose the Breather Hose. It lets the pressure in the tank remain equal to the pressure outside the tank at all times.

I agree. I am thinking it is a restriction as well. If it was totally blocked the fuel pump would not be able to overcome the vacuum. While out on a ride and you have used quite a bit of fuel does the tank seem to suck in when you open it to fill up? Might not be too noticeable.

 

[CBXRider]

I agree. I am thinking it is a restriction as well. If it was totally blocked the fuel pump would not be able to overcome the vacuum. While out on a ride and you have used quite a bit of fuel does the tank seem to suck in when you open it to fill up? Might not be too noticeable.

Yeah, the tank gasket is just the path of least resistance. No, it's the same slight swoosh, empty or full as long as it's warm outside. The hose is clear so whatever is clogging it up must be in the elbow the hose is attached to. Q Tip or pipe cleaner? No compressed air at home and I'd prefer not to remove the tank if possible.

 

[notright]

Not to beat a subject to death but, you might not be able to see the kink when you have the tank up but when you close it might be when it is getting pinched. You might want to pay careful attention to the routing and what is happening when you drop the tank,
Best of luck.

 

[jellyrug]

My dirt bike has done that for as long as I can remember. I'm waiting for the day it starts whistling a tune.