99 Fatboy fuel tank venting system
Thread Starter
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Road Warrior
Joined: Apr 2018
Posts: 1,347
Likes: 820
From: Moneta, Virginia
99 Fatboy fuel tank venting system
The manual shows a Vapor valve clipped onto the swing axis frame member... Damned if I know what a swing axis frame member is. I cant find anything that looks like a Vapor valve.
What I do have is a vent line going to a straight coupler that clips onto the frame under the seat. Its just a straight line that vents out above the oil bag.
In addition to the crossover fuel line at the front of the tank, the gas tank has two 1/4? nipples on the right tank and one 1/4? nipple on the left side tank.
How do these tank vents connect?
Do I need a Vapor valve?
What I do have is a vent line going to a straight coupler that clips onto the frame under the seat. Its just a straight line that vents out above the oil bag.
In addition to the crossover fuel line at the front of the tank, the gas tank has two 1/4? nipples on the right tank and one 1/4? nipple on the left side tank.
How do these tank vents connect?
Do I need a Vapor valve?
Dirt don't hurt
Joined: Jan 2011
Posts: 21,065
Likes: 4,561
From: Haslet Texas
The manual shows a Vapor valve clipped onto the swing axis frame member... Damned if I know what a swing axis frame member is. I cant find anything that looks like a Vapor valve.
What I do have is a vent line going to a straight coupler that clips onto the frame under the seat. Its just a straight line that vents out above the oil bag.
In addition to the crossover fuel line at the front of the tank, the gas tank has two 1/4? nipples on the right tank and one 1/4? nipple on the left side tank.
How do these tank vents connect?
Do I need a Vapor valve?
What I do have is a vent line going to a straight coupler that clips onto the frame under the seat. Its just a straight line that vents out above the oil bag.
In addition to the crossover fuel line at the front of the tank, the gas tank has two 1/4? nipples on the right tank and one 1/4? nipple on the left side tank.
How do these tank vents connect?
Do I need a Vapor valve?
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,116
Likes: 7,640
From: Poolville
That's the one I connected a 3/16 pneumatic air line to and stuffed it down the center post of the frame under the seat....This way if fuel ever did come out the vent it would go straight to the ground and not the motor or trans...
Seasoned HDF Member
Joined: Jun 2015
Posts: 10,291
Likes: 7,773
From: West Central FL
The manual shows a Vapor valve clipped onto the swing axis frame member... Damned if I know what a swing axis frame member is. I cant find anything that looks like a Vapor valve.
What I do have is a vent line going to a straight coupler that clips onto the frame under the seat. Its just a straight line that vents out above the oil bag.
In addition to the crossover fuel line at the front of the tank, the gas tank has two 1/4? nipples on the right tank and one 1/4? nipple on the left side tank.
How do these tank vents connect?
Do I need a Vapor valve?
What I do have is a vent line going to a straight coupler that clips onto the frame under the seat. Its just a straight line that vents out above the oil bag.
In addition to the crossover fuel line at the front of the tank, the gas tank has two 1/4? nipples on the right tank and one 1/4? nipple on the left side tank.
How do these tank vents connect?
Do I need a Vapor valve?
The left side tank vents through the right side tank which then vents to that vapor valve via a rubber hose thus eliminating the need for a vented gas cap. Big mistake.
I was having trouble with my tanks not venting because my vapor valve must have gotten plugged up and gas was being forced past my needle and seat causing the carb bowl to overflow. The cure was to shoot air through the hose that connects to the vapor valve and pop the hose off of it. Then I bought a pair of aftermarket gas caps that had the right side vented. Problem solved.
Thread Starter
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Road Warrior
Joined: Apr 2018
Posts: 1,347
Likes: 820
From: Moneta, Virginia
I found the Vapor valve; left side clipped to the swing arm pivot.
The line to the top fitting has been disconnected, the lower line pokes out to the ground.
The continuous venting system vent line connects at the tank and then through a couple fittings, changing from a hard plastic tube to rubber air line, then pops out on top of the oil bag.
I like 98hotrodfatboys idea of routing that line through the down tube to the ground... Seems safer than the top of the oil tank!
Thanks for the education on this... the manual isnt very clear
The line to the top fitting has been disconnected, the lower line pokes out to the ground.
The continuous venting system vent line connects at the tank and then through a couple fittings, changing from a hard plastic tube to rubber air line, then pops out on top of the oil bag.
I like 98hotrodfatboys idea of routing that line through the down tube to the ground... Seems safer than the top of the oil tank!
Thanks for the education on this... the manual isnt very clear
Dirt don't hurt
Joined: Jan 2011
Posts: 21,065
Likes: 4,561
From: Haslet Texas
I found the Vapor valve; left side clipped to the swing arm pivot.
The line to the top fitting has been disconnected, the lower line pokes out to the ground.
The continuous venting system vent line connects at the tank and then through a couple fittings, changing from a hard plastic tube to rubber air line, then pops out on top of the oil bag.
I like 98hotrodfatboys idea of routing that line through the down tube to the ground... Seems safer than the top of the oil tank!
Thanks for the education on this... the manual isnt very clear
The line to the top fitting has been disconnected, the lower line pokes out to the ground.
The continuous venting system vent line connects at the tank and then through a couple fittings, changing from a hard plastic tube to rubber air line, then pops out on top of the oil bag.
I like 98hotrodfatboys idea of routing that line through the down tube to the ground... Seems safer than the top of the oil tank!
Thanks for the education on this... the manual isnt very clear
You have to overfill your tank then lean it over before you have any chance of getting fuel out that tube.
I did manage to do it once.
When I had mine vented to the ground in front of my rear tire I filled up while holding the the bike straight up.
When I left the gas station I did it kinda fast and leaned way over to the right and the fuel that came out caused my rear tire to lose traction for a bit but I didn't go down but it was eye opening.
That OEM vapor valve that harley uses is a one way valve in other words it will suck air in but it will never let fuel out.
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Thread Starter
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Road Warrior
Joined: Apr 2018
Posts: 1,347
Likes: 820
From: Moneta, Virginia
Its been 25 years since I had a two piece tank. If I remember correctly arent you supposed to fill the right side tank first, then the left side?
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Dirt don't hurt
Joined: Jan 2011
Posts: 21,065
Likes: 4,561
From: Haslet Texas
The crossover is so small that the amount of fuel that crosses over while fueling isn't enough to worry about IMO.
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Joined: May 2008
Posts: 21,175
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From: South Carolina