Ok so started heritage yesterday for the first time since the fall, it started right up , let it run for about 15 - 20 mins to bring up to temp. Suddenly the idle began to drop below normal and when i twisted the throttle it sounded like it wasnt getting enough fuel. Shut her down and noticed a hissing coming from the gas tank vent hose that drops down thru near the swing arm , took the gas cap off and the vent stopped hissing but noticed that while looking at the crossover port inside the tank it was purging air bubbles???? Put the cap back on and the vent started hissing again very noticable and somewhat loud never heard that before ever . Now i will admit that i only had about half a tank of gas , i forgot to top off in the fall. My thoughts are is my gas cap clogged and not venting thus preventing fuel from crossing over when warm maybe that in addition to a half empty tank?? The heritage is an 04 and is fuel injected . thanx all CW

 

What year is it?

Also the HD Heritage does not vent thru the Fuel Cap but has a separate vent line located on top center of the gas tank running down the front of the tank to the bottom of the bike..

Sounds like a mud dobber made a nest in the bottom of the vent line under the bike.

 

Like he says, non vent cap..See if it will run with cap off. Probably setting all winter with rise and lowered temperature, the 3/4 empty tank sweated on the inside and there is water in it. Either a small bottle of gas dry measured correctly for a tank of fuel or ethanol gas will fix it. Mine got a dose of water and would not idle without holding throttle. I spent couple weeks messing with it before the second fill-up fixed it. Gas dry is nothing but alcohol. It will absorb water and take it on through engine. There is also a relief pressure valve in the tank that is probably what you heard with low fuel level. Once running, the fuel-pump runs all the time relieving pressure below 60PSI or so. It maintains that from idle to WOT. I doubt the line is stopped up. It's hard to believe a muddobber in the winter..let alone in a vented fuel line but I guess it could.

 

The Harley has two vents, the gas cap is vented in.
And you have the vent on the front of the tank runs down and there is a check valve on the end of the hose that vents out. The two work together to let the tank breath as gas expands, and as gas is used.
They also keep gas from spilling if the bike is dropped.

 

No what i heard is the fumes coming out of the vent line i know where the vent line is , nothing got into the vent line either. As far as the non vented cap i cant go with that recomendation every part search i do for a replacement cap for a 04 FLSTCI comes up as vented , the air bubbles i saw are inside the tank if you pop ur cap off and shine a lite down in there you will see where the crossover nipple is it was bubbling from there The fumes would stop gushing out the vent line when i took the cap off I just ordered i new cap for my year and model and it is a right hand thread VENTED cap all the non vented caps said left thread which i dont have on my bike . Bike has been inside all winter and humidity up here at 10000 feet is pretty much non existent except when it snows. Ill fill her up when i get chance and maybe put some dry gas in there hope thats all it is .

 

Search here on a Harley site, never seen a vented fuel cap on a FI bike or even referred to as vented.. That is what the hose is for. The top is sealed. However, I would like to see that if I am wrong. Is it cause you are up so high? http://partsfinder.onlinemicrofiche....-TANK-ASSEMBLY

 

Yeah im confused as well i took the cap off thats on there now and you can see the vents on the underside of my cap also you can see where the rubber gasket compresses on the filler tank hole the vented part of the cap doesnt even touch the tank it sticks up 3/8 of an inch off the tank.

 

OK guys read this post, then take your gas cap and put it to you mouth and blow, the suck in and see what it does.
Vented in not vented out.
That is what the front vent does, vents out.

 

And in the fuel injected bike there is a return hose (i believe) that leaks that is where your bubbles are coming from, that needs to be replaced.
Do a search for fi hose leaks.

 

The one question I see that has not been answered is:

Does the bike idle properly when the cap is removed?

If so try slamming your cap on a piece of wood and try idling again with the cap on. I have seen the valve in the cap stick before. For piece of mind, replace the cap if the bike idles properly with out it.

And yes, as stated before, the caps are vented.