where is the fuel tank vent - 800A

[su1kil]

Google is not much help here, so I am asking on this forum. Where the heck is the gas tank vent, and how does it work? Flip the fuel cap, I see one hole almost in the middle of the cap right below the locking mechanism, and another hole next right to the tank open near the hinge. I also see a pipe inside the fuel tank, and it looks like it is connected to the hole near the hinge. I hear the tank making sound, so that is when the gas comes out. Also, as the gas level goes down, the air needs to go in the tank, right? How is it done?

[Classic]

The vent itself is in the gas cap and it works with the hole you noticed in the rim of the tank opening. If you get a squirt bottle of water and shoot it into the hole, it will run out of one of the rubber hoses that hangs down under the middle of the frame. Always cover the opening of the tank with a rag or something to prevent stuff from going into the tank.

[su1kil]

The vent itself is in the gas cap and it works with the hole you noticed in the rim of the tank opening. If you get a squirt bottle of water and shoot it into the hole, it will run out of one of the rubber hoses that hangs down under the middle of the frame. Always cover the opening of the tank with a rag or something to prevent stuff from going into the tank.

A-ha, so the air goes up into the rubber hose, the (copper?) pipe inside the tank, the hole by the rim, to the cap, finally the center hole under the cap?
Did I get it right?
If I am right, the rain drop from the sky on the tank cap cannot cause the clog. But if the water splash from the road gets into the rubber hose, do you think it will cause the vent passage to clog?
I had some trouble with gas supply yesterday under fair rain, and I would like to understand the mechanism better...

[Classic]

Yeah, that's it and what some do is identify the correct vent hose and route it into the right side cover thereby keeping it out of harms way. Of course, if you overfill the tank then the excess runs into (and out of) the side cover area so don't overfill the tank. The vent in the gas cap of my 800A was defective to I removed it out of desperation. Not recommending you do that as there is the risk of gas running out if you lay down the bike but I can say that once the vent was history, so were the venting related problems.

[su1kil]

oh my... then that means that some water got into the fuel tank? I should put some SeaFoam in the tank...

[zphreaky1]

oh my... then that means that some water got into the fuel tank? I should put some SeaFoam in the tank...

It doesn't hurt, but I wouldn't think you got a lot of h20 in there unless you left it open during a heavy rain. A drop or two isn't going to kill it, but then again seafoam--good water--bad
I was thinking of the vent when you said it has happened before, not just the time it rained, and I'm not sure about a clog, though it can happen, I think you need to worry more about a kink. Do a search here, I'm not sure if there has been a lot of discussion about it, as I am new here, but I know there is some stuff in the VROC archives so you can try that too.

[su1kil]

It doesn't hurt, but I wouldn't think you got a lot of h20 in there unless you left it open during a heavy rain. A drop or two isn't going to kill it, but then again seafoam--good water--bad
I was thinking of the vent when you said it has happened before, not just the time it rained, and I'm not sure about a clog, though it can happen, I think you need to worry more about a kink. Do a search here, I'm not sure if there has been a lot of discussion about it, as I am new here, but I know there is some stuff in the VROC archives so you can try that too.

Yes, I had it before. I do not remember clearly, but it may be the gas being too full. For the kink issue, where do I want to start? Any specific hose in your mind? Thanks for your help..

[zphreaky1]

yeah the tank vent hose. make sure it's not kinked, just find it and follow it from beginning to end and make sure it looks good. Did you do the search for the mod? I'm a few years removed from the 800 but that is what it sounds like to me.

[su1kil]

Yeah, that's it and what some do is identify the correct vent hose and route it into the right side cover thereby keeping it out of harms way. Of course, if you overfill the tank then the excess runs into (and out of) the side cover area so don't overfill the tank. The vent in the gas cap of my 800A was defective to I removed it out of desperation. Not recommending you do that as there is the risk of gas running out if you lay down the bike but I can say that once the vent was history, so were the venting related problems.

Yep, I found the hose running right hand side from under the tank. I blew at the end of the hose and the air came out of the hole with the cap open. I put the end of the hose inside the storage box.
I am not sure if the splash clogged the hose from the bottom, or if the rain drops around the fuel cap was pushed to the hole where the cap and tank meets. I did not have the windshield, and from looking at the angle, I think the rain and wind will hit the cap area very hard. I closed the cap and pushed it down. The cap moved down on the springs maybe about 2 - 3 mm. Maybe the seal around the vent hole is not that good, allowing the water to get in from outside. Yesterday the first 4 miles under 35 mph was just fine. Once it made 50 mph about half a mile, the engine started loosing.
By the way, I took out the two philips screws and checked the inside. It looked pretty clean. Which part did you remove exactly?

[zphreaky1]

go to vroc.org and do a archive search on 800 tank vent or something and it should have a thread with the mod described

[Classic]

When mine would start acting up it was as though the bike was running out of gas but it wasn't. This would only occur at higher speeds when fuel delivery was at it's greatest rate. When it would start to die, if I pulled off the road and opened the gas cap slowly I would hear air being sucked into the tank which is how I figured out what was happening. If I relieved the vacuum by opening the cap, the bike would start right up. I doubt you got any water in the tank and a little probably wouldn't hurt anything on such a regular basis anyway but Seafoam is never a bad idea. I don't recall the exact parts I removed but I think it was anything not related to the latch. As I recall there was a little pointed brass piston and some little spring inside a diaphragm thingy. It was a little tricky to reassemble so watch the parts location when to take it apart, if you do. Once I removed all that stuff the bike ran perfect but remember there is the possibility of a fuel spill if you drop the bike with the stuff removed.

[E-J]

IF the seal on the cap is good and the cap is aligned, there is no way for water to travel up the hose nor migrate up under the seal. The opening to the tank is a qtr inch higher than the tank and there fore higher than the little well around the fuel fill opening which is designed to catch over fill and drain without coming in contact with the engine. If there is water or fuel in the well, it will blow back against you when you ride even at slow speeds.

[su1kil]

IF the seal on the cap is good and the cap is aligned, there is no way for water to travel up the hose nor migrate up under the seal. The opening to the tank is a qtr inch higher than the tank and there fore higher than the little well around the fuel fill opening which is designed to catch over fill and drain without coming in contact with the engine. If there is water or fuel in the well, it will blow back against you when you ride even at slow speeds.

The rubber gasket between the cap and the tank seems to be tight, and I agree with you that the water cannot go through it to the tank. How about the vent hole right by the hinge, outside of the rubber gasket? It is raised up from the tank, so this helps. However I am not sure if the cap is making tight contact on the vent hole. W/o windshield, if I look at the cap area from the front of the bike horizontally, I can even see the outer clearance between the cap and tank. The shape of tank will affect it too. I can imagine the possibility that the rain drop or the light mist from the road going under the cap violently passing by the vent hole. What if there is gap between the cap and the vent hole? I will check again, but if there is no rubber or spring component for the vent hole, the contact cannot be insured, I think... Let me know if I got it wrong. I would rather be wrong.

[su1kil]

When mine would start acting up it was as though the bike was running out of gas but it wasn't. This would only occur at higher speeds when fuel delivery was at it's greatest rate. When it would start to die, if I pulled off the road and opened the gas cap slowly I would hear air being sucked into the tank which is how I figured out what was happening. If I relieved the vacuum by opening the cap, the bike would start right up. I doubt you got any water in the tank and a little probably wouldn't hurt anything on such a regular basis anyway but Seafoam is never a bad idea. I don't recall the exact parts I removed but I think it was anything not related to the latch. As I recall there was a little pointed brass piston and some little spring inside a diaphragm thingy. It was a little tricky to reassemble so watch the parts location when to take it apart, if you do. Once I removed all that stuff the bike ran perfect but remember there is the possibility of a fuel spill if you drop the bike with the stuff removed.

Thanks for the info.. After work this afternoon, let me post pictures of the tank cap. Once you see it, you could explain it to me no doubt.
Thanks...

[su1kil]

BTW, how high should I fill up the gas? I do not see any high level mark inside the tank...

[Classic]

To the bottom of the filler neck.

[su1kil]

To the bottom of the filler neck.

yeap that is what the manual said, but what is the filler neck?

[su1kil]

I took some pictures here.
Attachment 10854

This is when the fuel cap is open.

venthole.JPG

vent hole close up here.
The cone under the cap goes into the well on that tank, right? It does not look like it has a good seal between the cone and the well. If somehow water gets on the cone, and drips down to the end of the cone, the water could be sucked into the vent hole? Do not know...

Attachment 10856

right after taking out the two screws and the case.

Attachment 10855

this is as far as I could go. I did not try to take out the orange color rubbery stuff.

So, could anyone provide some insight about the modification?
Thanks,

[Classic]

It would be about three inches from a totally full nearly running over tank.

[su1kil]

It would be about three inches from a totally full nearly running over tank.

is the fillerneck some kind of marking or a part inside the tank ?