Noise ID'd--burping fuel tank

[coolwind57]

Ok so this has been going on since I first looked at this motorcycle to buy from the previous owner. After the engine was shut down, it would make a weird noise for a brief second or two, sometimes making the noise for up to 10-15 minutes. At first, I thought it was some electrical issue...maybe a small surge going to the horn or something. When asked about it, the PO simply replied, "That's her telling you she wants to ride some more." Funny.

Anyhow, it has taken me over a Month to figure it out. Guess what happens when I pull the gas cap? Yep, pressure releases and it stops making the noise. Dude, I'm burping my motorcycle now.

So this probably isn't very normal. Anybody know how pressure release is suppose to happen in these bikes?

I was thinking of pulling the seal inside the gas cap and lubing it up and reinstalling it. But besides that, do I have bigger fish to fry? Should I look at replacing the cap or perhaps the rubber line coming out of it? Maybe an obstruction somewhere?

My burping bike otherwise runs well. Absolutely no problem besides an occasional very light backfire when I jack up the rpm--that's probably due to the aftermarket stainless exhaust (mufflers).

Those in the know about belching gas tanks--spill your guts please.

 

[kiltman]

This normal, I always have a swoosh sound when I open the cap from the fuel tank.

 

[coolwind57]

This normal, I always have a swoosh sound when I open the cap from the fuel tank.

I'm not so sure what you read of my post is accurate.

The noise happens after I shut the engine down. You'll be sitting there talking with your bud and the bike starts to make this noise. It lasts for a second or two and then usually does it several more times....maybe a minute or two of normal quiet in between the noises. So, it does not happen when I open my cap--on the contrary, it STOPS when I open my cap.

 

[John OoSTerhuis]

It’s normal. The cap vents each way, pressure or vacuum, depending on conditions.

John

 

[coolwind57]

It’s normal. The cap vents each way, pressure or vacuum, depending on conditions.

John

Weird. The only bike I've ever owned that can make noises all alone by itself in an empty garage.

 

[SMSW]

If you want a fancy term for it use this: borborygmi

 

[John OoSTerhuis]

Mine’s been doing it for 25 years. Folks have been reporting this for ages. Some ST1100s do it more than others. It’s the diaphragm in the cap vibrating like a reed. Kind of a moaning sound. I can dig up a schematic of the cap’s innards if asked.

John

 

[Walleye]

Weird. The only bike I've ever owned that can make noises all alone by itself in an empty garage.

Glad this issue came up, has been buggin me for the last day and a half. Hadnt noticed any sounds but have a good sucking vacuum when removing the cap, I know some of the old bikes would get a vacuum lock and shutdown starved for fuel if the cap vent was blocked.

 

[ST Gui]

Do not believe these guys. It's not normal. It's the ghost in the machine! Get out of the garage now!!

 

[SMSW]

Did 1100's make this sound when new? If so, it is "normal", assuming a minor mistake on Honda's part when designing the fuel venting system. If they did not make these noises when brand spanking new, it is not so 'normal' and is probably due to a build-up of dirt in the venting system.

 

[Jim Van]

To check the two-way vent valve in the gas cap, remove the small vent hose from the barb on the gas cap, remove the cap and install a short piece of hose of the same size.

The check valve is a two-way valve. Blow & suck the other end of the short length of hose. You should have flow each way - it takes a bit of pressure / vacuum for it to work. If you want to do a bit of PM, remove the hose and spray some carb cleaner into the check valve, reconnect the hose and blow out the carb cleaner.

Also, check to see if the hose retainer on the side of the gas tank isn't compressing the hose. The one on my bike was. I got a longer screw and self-locking nut with a nylon insert to secure the retainer without compressing the hose.

BTW, if removing the gas cap didn't stop the noise, what you heard may have been a mouse farting. The cure then, would be to put out a trap to get that little bugger.

 

[Jim Van]

Do not believe these guys. It's not normal. It's the ghost in the machine! Get out of the garage now!!

Oh Yeah, some ST1100's are possessed. If you suspect this, call the local Catholic church and arrange for an exorcism. They are the experts. If you can get a priest from out of town, that would be even better. The expert is usually from out of town.

 

[Walleye]

Theres a small bee that will make a mud nest inside of any open tube, learned about this long ago from the outboard motor folks and have seen it many times, they will block the discharge tube of for the water pump.

 

[Upt' North]

No big fish here Coolwind, with a name like that you must be used to belching.
They'll sometimes do it hours later, I just say pardon.
You mentioned the filler cap, if it's tight put a little rubber grease on there. I said a little.
Upt'North.

 

[Bush]

You mentioned the filler cap, if it's tight put a little rubber grease on there. I said a little.
Upt'North.

Put that grease between the cap and rubber, not between the rubber and fuel tank. This "fix" for a tight cap will last much longer that way.

 

[John OoSTerhuis]

Did 1100's make this sound when new?

Yes. Mine did/STill does. Those of us who anthropomorphize find it quite charming.

Heh heh... “borborygmi”... gotta remember that.

John

 

[SMSW]

Yes. Mine did/STill does. Those of us who anthropomorphize find it quite charming.

Heh heh... “borborygmi”... gotta remember that.

John

Any doc will get a laugh out of that.

 

[tt48]

coolwind57, I really believe your bike is evil. In the interest of your safety, I can take it off of your hands if needed.

As far as bikes making noises in a garage all by themselves, it happens. My bike sat for a couple years and I swear there were times when I walked by it on the way to my cage, I heard the bike release a long, sad sigh.

Since I got her up and running again, I don't hear the noise in the garage anymore

 

[dkruitz]

Mine does it, most often on a hot day. I thought I was hearing things the first few times it happened, then I figured it out.

 

[coolwind57]

Well, I learned a little about this phenomenon within this post. But perhaps my most treasured lesson was the great new words I learned: "borborygmi" and "anthropomorphize". Wow.

At first, these new words made my brain bombinate too. But don't fret. Cachinnate, suspire and you're be eructing these new words out in no time.