Fuel Tank Venting (WTF? why two?)

RenoJohn · May 5, 2010

I could not find this on a search, if it has been covered previously ...i'm ready to accept my penance

Short question:

There are two vent tubes coming from the bottom of the tank. Why Two ....what is the logic? (and/or what am I missing?)

Long Question:

Like many I've had some venting/boiling gas/high pressure issues on hot (100+F) days when running the bike hard hard.

Today I was under the tank and curious about the venting. There are two vents -why?.

---And, what have others done to help relieve high pressure build up on the cap of the tank? I recall a few folks drilling small hole(s?) ..has this been documented anywhere.

Sidenote:

Trust me when I tell you that installing a 3/8inch bulkhead is CONSIDERABLY more difficult than doing a 1/4inch or even a 5/16inch .....it is truly on the edge of realistic options.

RadioHowie · May 5, 2010

RJ,

One is a true "vent", as in "vapor vent" through the cap assembly...the other is overflow to give excess fuel a path-to-ground when you're trying to squeeze an extra half gallon into the tank and run over.

Bustanut joker · May 5, 2010

First of all.. "what am I missing?" I could tell ya but, well we all know what it is. :****:

Secondly.. I'd help ya but I don't have a fookin clue.

That's why I hang here, plenty of fart smuckers who do..

:jester:

RadioHowie · May 5, 2010

Took me a few minutes to find it, but Fred W did a GREAT photo documentary on disassembling the filler cap and alleviating vapor overpressure HERE.

RenoJohn · May 5, 2010

RadioHowie said:
RJ,
One is a true "vent", as in "vapor vent" through the cap assembly...the other is overflow to give excess fuel a path-to-ground when you're trying to squeeze an extra half gallon into the tank and run over.

I had no doubt it would be a superior Gen1 owner who would have the technical aptitude to help here. OK, got it ...and it makes a bit of sense knowing that there is some drama going on up in that complex fill-cap. I think I'm going to "Y" these two vents together a foot or so below the tank and go into just one tube ...replacing much of the high dual tube baggage with just one tube going to the bottom of the bike.

Thanks RH, appreciate the skewling.

Bustanut joker said:
First of all.. "what am I missing?" I could tell ya but, well we all know what it is. :****: Secondly.. I'd help ya but I don't have a fookin clue.

That's why I hang here, plenty of fart smuckers who do..

I'm with ya man ...ever notice all the smart guyz are on Gen1's? Too much smart is no good, and thank goodness there's you's and me's to balance their shit out.

RadioHowie said:
Took me a few minutes to find it, but Fred W did a GREAT photo documentary on disassembling the filler cap and alleviating vapor overpressure HERE.

OH MAN, ain't that the bomb!!

So, me taking out that stupid T-Lock and so I can immediately remove the key -Jeeze that has been on my want list for the last 70thousand miles. And I'll remove that stupid catch-valve ball bearing which will greatly help the likely venting drama.

OH SHIT!! wait, i can't do either of those! I've already used up my weekly allotment of "free Fred advice".

I'm either going to have to do some good karma, -or wait until next week. Seriously Howie, the guy bailed me out of some electrical chaos yesterday that would have warped time travel the wrong way had Fred not thrown some mentoring reno way. Yep, even the farm animals were covering their eyes when they saw my schematic.

RadioHowie · May 5, 2010

RenoJohn said:
And I'll remove that stupid catch-valve ball bearing which will greatly help the likely venting drama.

Just remember, that little valve ball is there to keep gas from running out when you turn the bike upside-down for oil pan cleaning, so empty the tank first. :thumbsup:

RenoJohn · May 5, 2010

RadioHowie said:
Just remember, that little valve ball is there to keep gas from running out when you turn the bike upside-down for oil pan cleaning, so empty the tank first. :thumbsup:

Ya, I'm factoring that in my decision. I'm familar with tip valves, In fact I put one in my new fuel cel:

but in the case of the primary tank, I think the venting drama that likely will be alleviated by removing the bearing far out-weighs a trickle of gas that *might* come dribble out when I have the bike upside down to change the oil pan gasket

...or when the bike is on it's side from a get-off ....in which case I'm likely to have bigger issues than a bit of spilled fuel.

wfooshee · May 5, 2010

RadioHowie said:
Took me a few minutes to find it, but Fred W did a GREAT photo documentary on disassembling the filler cap and alleviating vapor overpressure HERE.

I knew I'd seen that, but couldn't find it. I was looking for a thread, not a post, I guess. (So much for Search-fu, huh?) I've had some hissing the last few times I've opened the gas cap, haven't determined if it's blowing or sucking, but I think it's blowing. Took the cap apart Sunday from what I remembered of that post, cleaned everything (it needed it!) and put it back together, with the ball bearing check valve.

Space on the tank under the cap assembly was fairly clean, vent tube was clear, figured I was good to go.

At the gas station today, hissing when I opened the cap. Shit! guess I'll go back and take that ball out and see how it goes.

RenoJohn · May 5, 2010

wfooshee said:
......... Took the cap apart Sunday from what I remembered of that post, cleaned everything (it needed it!) and put it back together, with the ball bearing check valve.
Space on the tank under the cap assembly was fairly clean, vent tube was clear, figured I was good to go.

At the gas station today, hissing when I opened the cap. Shit! guess I'll go back and take that ball out and see how it goes.

I'm with you wfoosheeter

I'm not saying that maintenance and cleaning are bad things for the cap-assembly,

...but what you say here reinforces my feeling about the cap:

There is something fundamentally wrong with the design, ...and for me, that bearing is coming out.

dcarver · May 5, 2010

RadioHowie said:
Took me a few minutes to find it, but Fred W did a GREAT photo documentary on disassembling the filler cap and alleviating vapor overpressure HERE.

Freaking impatient Noobies with Gen1 IQ's - 2 words RJ, SEARCH FUNCTION! Jeesh. Some old dawgs just can't learn new tricks. What's a feller to do with a Gen 1 guy? Oh, that's right, send him off to BustaNut, followed by Odot, and then RadioHowie. :rofl:

RadioHowie said:
RenoJohn said:

And I'll remove that stupid catch-valve ball bearing which will greatly help the likely venting drama.

Click to expand...

Just remember, that little valve ball is there to keep gas from running out when you turn the bike upside-down for oil pan cleaning, so empty the tank first. :thumbsup:

Or when playing Flipper like your lover SkooterG!
Hugs n Kisses!

:****:

:lol:

Sounds like your making good progress converting the new old bike into a LD ride RJ - keep up the good work, wanker.

Harald · May 6, 2010

RenoJohn said:
RadioHowie said:

RJ,
One is a true "vent", as in "vapor vent" through the cap assembly...the other is overflow to give excess fuel a path-to-ground when you're trying to squeeze an extra half gallon into the tank and run over.

Click to expand...

I had no doubt it would be a superior Gen1 owner who would have the technical aptitude to help here.

If I recall correctly, those of us with Gen II bikes only have one vent hose to disconnect.

And what's up with that foil glued to the tank bottom like some redneck has been working on the bike?

Gen II bikes come from the factory with a heat shield installed on the bike! No roasting nuts! :yahoo:

Perhaps Gen I bikes aren't superior?

Ducking and running.....

RadioHowie · May 6, 2010

Harald said:
RenoJohn said:

RadioHowie said:

RJ,
One is a true "vent", as in "vapor vent" through the cap assembly...the other is overflow to give excess fuel a path-to-ground when you're trying to squeeze an extra half gallon into the tank and run over.

Click to expand...

I had no doubt it would be a superior Gen1 owner who would have the technical aptitude to help here.

Click to expand...

If I recall correctly, those of us with Gen II bikes only have one vent hose to disconnect.

And what's up with that foil glued to the tank bottom like some redneck has been working on the bike? Gen II bikes come from the factory with a heat shield installed on the bike! No roasting nuts! :yahoo:

Perhaps Gen I bikes aren't superior?

Ducking and running.....

Us Gen I'ers don't have to take off an aluminum blankee like you Gen II toddlers to work on our superior machines. :blum:

Big-B · May 7, 2010

RenoJohn said:
I could not find this on a search, if it has been covered previously ...i'm ready to accept my penance
Short question:

There are two vent tubes coming from the bottom of the tank. Why Two ....what is the logic? (and/or what am I missing?)

There was some discussion on a thread by Joe2lmaker about two tubes on the Gen I fuel pump. Are these vents related to that? clicky

RadioHowie · May 7, 2010

QUOTE (Big-B @ May 7 2010, 01:21 AM) <{POST_SNAPBACK}>
There was some discussion on a thread by Joe2lmaker about two tubes on the Gen I fuel pump. Are these vents related to that? clicky
Not the same thing....Joe2 was referring to the two fuel nipples, output/input, on the Gen I fuel pump.

RenoJohn was talking about the two steel hose connectors located at the left/rear/bottom of the fuel tank.

twodogs · May 7, 2010

RenoJohn said:
but in the case of the primary tank, I think the venting drama that likely will be alleviated by removing the bearing far out-weighs a trickle of gas that *might* come dribble out when I have the bike upside down to change the oil pan gasket ...or when the bike is on it's side from a get-off ....in which case I'm likely to have bigger issues than a bit of spilled fuel.

"Likely" perhaps, but perhaps not. That bit (or more) of spilled fuel may become your or your family's nightmare. I know I'm something of a one note Johnny on this but I've seen the results of fuelcap leak gasoline fires on humans - one tractor operator and one motorcycle passenger - and they were horrific. One died, the other didn't. I'm still not sure which I feel sorrier for. Thinking about it now,... the one that lived.

But, this is America. Your choice. Me, no way I'd **** with it.

Bill

Fuel Tank Venting (WTF? why two?)

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