[MBFsupport]

Yea I get that way sometimes but I'm talking about my gas tank :? I filled up for a rally ride and went and parked and got ready to go. We didn't leave for about an half hour and it was kind of a hot day. As soon as soon as I stood the bike up gas started puking out of the gas cap :evil: Got any ideas how to fix that?

 

[JonUkman]

Vented Gas Cap

(Lamont, I know you already know this but maybe it will help someone else.)

The '97 model year and earlier used a vented gas cap (designed to vent both the pressure and the expansion of gas as it heats up and expands inside the tank) instead of the later (and current) vent port and overflow tube setup.

I hate to state the obvious, but most faced with your situation, will probably fill-up just before the start of the ride, and shouldn't fill the tank quite as full. Rapid acceleration (launching up an on-ramp) while the gas tank is full, will cause the gas to escape through the vented gas cap.

Probably not a practical solution, and I have never heard of anyone who did it, but you could modify your tank to include the vent hole set-up and then install a non-vented gas cap.

While on the topic, watch out for overfilling the 2000 and earlier model year reserve gas tanks--stop short of "near the top". They also incorporate the vented gas cap design and will puke gas when full and the clear coat on your rear fender, just below and back of the reserve gas cap, will yellow very quickly, and in my experience, it will not buff out.


Jon Ukman
www.EBossHoss.com

 

[hossbuilder]

Gas Tank Vent

Lamont,

Here is my solution to the early tank situation. Drill a hole in the right side crossover fitting and sweat a copper tube in it. Make the tube long enough so it just about touches the top of the tank. Now change to a non-vented gas cap.

I have a picture of this fix. But...I have never learned how to incorporate a picture into these posts?????? It won't let me paste an image and I don't have these pictures stored on a web accessible site.

 

[hossbuilder]

Reserve Tank Vent

OOOPS! I just read Jon's post.

I also have a fix for the early reserve tanks\ to vent them so you can run a non-vented cap. I ruined my very first Cris Cruz paint job with the rear tank puking on the rear fender. The bike was in a hot trailer on the way to Sturgis and it curdled the paint right down to the primer.

I wish I knew how to incorporate a picture so you could all see the fixes.

 

[V8soundlover]

Re: Reserve Tank Vent

I wish I knew how to incorporate a picture so you could all see the fixes.

Neil, glad to be able to do something for you. I saved all your pictures on my harddisk. I did it exacly like you did, and I never had only one drop of gas on my tank. Lamont - here are Neil's pictures of his early-model gas tank vent. Put a hose over the small vent tube, line the hose somewhere to the ground, put a small gasoline filter between (to prevent sucking debris)- and you will have no puking anymore.

Puuuh...just back from a 3 week vacation..guess I've got a LOOOOT to read.

 

[V8soundlover]

There is a cure for gas running out your overflow . It's called a Neil Weber designed tank vent . I had the same problem with gas running out the vent hose and not able to fill the tank to it's capacity so I made one for my Boss and I know Olaf made one for his . I can fill my tank now right to the top with no over flow and it vents and runs perfect . If I was more of a computer whiz I'd post some pictures of the Weber style vent but I know Olaf can do it . It is a real neat set up . How about it Olaf .

Jack

This post subject is exactly one year ago. In the meantime I changed the (good working) brass proto-type fuel tank vent to a better looking one. I choosed a 1/4" NPT steel elbow-fitting, because I wanted to use Aeroquip braided SS hose with AN connectors for both - cross over and tank vent hose. I drilled the fitting for a 0.20" outside diameter stainless steel tube, which I bend to 90 degrees. For the tank vent outlet I used a smaller, straight steel fitting, machined it to fit on the 0.20" tube, brazed everything together and took it to the chromer. The fuel crossover is a 6AN, while the tank vent has a 4AN connection. For the other side of the tank I used a common nickel plated, 6AN 90 degree, aluminum 1/4" NPT elbow fitting. I bought all parts at Summit, except the 0.20" SS tube. Here are some pics of the new setup:

 

[HogV8]

Thanks Olaf , does it work as well as mine ?

Jack

 

[V8soundlover]

Jack,
yes, it works perfect. No puking gas out of the fuel cap, even in the
hottest summer days. But what I like most is - no excessive pressure
build up in the tank like before. The 99 and earlier Bosses had no vent
except the gas cap, and when I opened the gas cap at summertime it
always reminded me to the noise a well shaked Coke bottle produces,
when opened. I was always afraid the pressure could flood the
engine when the bike was standing in the sun for a while.

Loaf

 

[HogV8]

Olaf . my vent works perfect also . I also epoxied the vent in the gas cap shut so there is no possible leakage there . I can fill my gas tank up right to the bottom of the bung now because my vent tube extends up along side of the bung to the absolute highest point of the tank with no leakage from the vent hose or the cap .

Jack

 

[Glenn B]

Loaf,
That "built up pressure" can be a life savor when the fuel pump craps out. Gives a little pressure to bypass the pump and get you off the highway. Been there-done that, more than once.
Glenn

 

[V8soundlover]

Glenn,
never thought about that. Have you ever had to ride for a long distance
without fuelpump? I've heard the gravity feed would bring us home, but
we can't go fast. Is that right? I always carry an "emergency hose" for
bypassing the fuel selection valve and pump if needed (tank to carb
direct). But I never had to use it, therfore I don't know if it will work in
case of a bad fuel pump.


Loaf

 

[HogV8]

I carry the stock fuel pump for a spare with some hose to bypass my Holley pump if need be . Doesn't take up much room in my tool box under the seat .

Jack

 

[Glenn B]

Olaf,
I have had no luck on the gravity feed. I get a little pressure form my "unvented" system if it is warmed up enough to just get me slowly off the highway. I carry a spare carter barrel pump, short section of fuel line and electrical connectors to fix on the side of the road. I have only been able to get approx 25-29K miles on the rotary vein pumps. (Holly, Mallory) I have changed more than once on the side of the road.
Glenn

 

[Zenbiker]

Not sure I get this problem. I have a 2000 which has an overfow tube that exits at the bottom of the bike. (doesn't everyone have this?) The tube originates from below the cap and simply ends up on the floor. If I overfill the gas goes out there and never through the cap. I have Landmark stainless caps but even before I put these on the gas would go through the overfow tube. The reserve tank, on the other hand, will puke onto the rear fender if I overfill because there is no overflow tube.
Don't loop the tube as I was told to do once because that episode resulted in overfow. Just route it directly down from the filler neck to the floor. the liquid will find it's lowest level as always...Joe

 

[HogV8]

Joe ,

That is the same vent I had on my 2000 gas tank and the reason I changed to the Weber style vent was I could never fill my gas tank . If I did try to fill it, gas would run out the vent tube all over the ground under the bike in a big puddle . Not Good . Now with the original vent tube under the gage panel plugged and the new Weber style vent , I can fill the tank to the bottom of the bung and not have to worry about gas running out the vent onto the ground or out my gas cap because I epoxied the vent in the cap closed . Another plus is now my tank will hold 8 1/2 gallons instead of only 7 1/2 gallons . I know it's not a big deal to be able to get another gallon of gas in my tank , but believe me I feel much safer with my new set up . Never did like the idea of starting my bike over a puddle of gas so if it did happen I would have to push it out of the puddle to start it and look like idiot doing so with a group of people watching me .

Jack

 

[buyarbi]

I have been havig problems with fuel comming out of my vented gas cap since I got the bike. Only one time did I fill up and have the gas run out of the overflow. So I have been trying not to fill so much. Every once in a while though it is to full and I am going around a right hand curve and suddenly have a spray of gas coming out of the vented cap. If I plug up the vents on the cap will it matter since there is a vent line in the tank. I have 2002/350 no reserve tank.

Bill

 

[Adrian]

I must be missing something about the vented caps. Every Boss Hoss I have seen has a vent hose so there fore you need a vent in the cap like a hole in the head. I know the Boss Hoss factory gives us vented gas caps (and that is dumb) because they will leak out and ruin the paint.
The first thing I do is get some JB weld and plug the vent holes. We already have 1/4" holes in the vent hoses.
Help me out here.

Adrian

 

[MBFsupport]

I must be missing something about the vented caps. Every Boss Hoss I have seen has a vent hose so there fore you need a vent in the cap like a hole in the head. I know the Boss Hoss factory gives us vented gas caps (and that is dumb) because they will leak out and ruin the paint.
The first thing I do is get some JB weld and plug the vent holes. We already have 1/4" holes in the vent hoses.
Help me out here.

Adrian

Mine has no vent at all in the tank other than the cap. I will change that this winter.

 

[HAWK88]

Tank Vent

Lamont,

My 97 tank is the same as yours, and is on a "round 2 it" list.

HAWK88
Jack Phillips