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Hi all.


While removing the alternator on my 2007 GL1800 (took me 20min.) I found a T-piece on a tube, the tube is to remove fuel from the canister (when fueltank is overfilled).

I didn't find ANY other tubes nearby which should connect on that T-piece and I don't think it's there to give extra air to the tube so I wonder why this piece is mounted there.

Since it is an open T-piece fuel is dripping down the tube and could escape trough the T and the T is near the alternator so I want to eleminate the T or close it to avoid fuel leaking near the alternator.

A suggestion from my Dutch fellows on a Belgian forum is that this piece could be for American models which have extra fuel emmission parts which then connect also the this fuel drain tube.

So my question is, for what is this piece and can I simply remove it to avoid leaks near the alternator or should it stay there to give extra air to the tube?

Many thanks in advance for a quick answer since I want to mount the alternator back asap.



I also searched for a drawing and partnumber of this piece (to know the description) on hdlparts but didn't find it.

Pierre

 

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It's too big for an air tube. I suggest attaching a piece of fuel or light fish tank hose to the open nipple, and run it down to where the other drain hoses go.
 

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Thx for the advice but as curious as I am I still want to know why it is there ;-)
 

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That does not appear to be something that came on the bike. Did you buy it new or used? I looked in the manual and could not find that piece.
 

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The bike is not new bought, from 2007 but the previous owner has only had the bike for 3000 miles so actualy it is a brand new bike and not tampered with. Couldn't see why they would change this so in my opinion it was there from start on and yes, it is a plastic piece. If some other readers would remove the left plastic cover and look behind the alternator for the FUEL DRAIN TUBE (not the coolant overflow) and could state they have some other tube attached to it or not that would be helpfull to know if it is a American/Europe thing only. I'm not sure if a model year could be different but I would say only 2006 and later...


Again, it looks very original and can't see why this would have been added afterwards for any reason, regarding the milage and the state of the bike (only a few chrome addons)...
 

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N°2 is the part. Would you American fellows be so kind to look if a tube is attached to this connector and where it leads to? I'm very curious ;-)

The tube functions as a airbreather for the fuel tank.



N° 24 is the tube for fuel overflow.
 

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I was just paging through and ran across your thread for the second time by accident. I think I know what it does. I bet in most cases it does nothing. In the unusual case of extreme overfill orgoing down a steep hilletc. that hose could siphon for a while. I bet the tee is an air break to prevent siphoning from the vent hose. What da ya think?? :? :? :?
 

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I will try to remember to take a look at that tomorrow.
 

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That IS the vent hose in the diagram. Just had my fuel tank out (2007 gl1800) and don't recall seeing anything like that)
 

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Well, someone over here called Honda and solved the mistery; the piece is placed there because turbulence under the motorcycle (where the tube ends) could cause pressure in the tube to the tank. So if pressure builds up below it vents trough the open connector. EVERY GL1800 should have this to avoid problems with pressure in the fuel tank.

Regards, Pierre
 

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That piece doesn't show on the 2007 diagrams, nor is it in actuality in place on the bike. On the models outfitted for U.S. emission standards that tube goes directly to the evaporative emissions canister which in turn passes the flow back to the crankcase via a purge valve. No open end to that tube, though the canister does have a drain tube on it. Sinse you have produced a diagram which clearly shows it, but on an earleir model, are you certain you are on a 2007 model year bike? On my 2007, there are just two hoses in the area you show in your picture. One is the vent tube forom the coolant overflow tank, and the other is the drain tube from the spillage tray that surrounds the fuel filler hole/gas cap.
 

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I am not sure who gave you the info about pressurizing the fuel tank but I have my doubts. It is normal to have either pressure or vacuum in a fuel tank and it would not be an issue. The EVAP system is designed to deal with either. If the bike has no EVAP system it would make no difference as the pressure would vent out the cap. Also in the case of having an EVAP system there would be check valves that would eliminate the possibility of pressure being introduced in that way. I still think it stops siphoning in case of overflow.
 

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redwing52 wrote:
I am not sure who gave you the info about pressurizing the fuel tank but I have my doubts. It is normal to have either pressure or vacuum in a fuel tank and it would not be an issue. The EVAP system is designed to deal with either. If the bike has no EVAP system it would make no difference as the pressure would vent out the cap. Also in the case of having an EVAP system there would be check valves that would eliminate the possibility of pressure being introduced in that way. I still think it stops siphoning in case of overflow.
Well, the source came from someone who works at the Honda factory in Belgium and I can't see why this explanation would be doubtfull.



The piece is there for a reason and the explanation is plaussible so I am OK with that. You could easyly test it yourself, if you don't have the T connector close the tube and drive for a few miles. My guess is your bike will have problems to get fuel in the injectors. So if enough turbulence is made under the bike and it keeps the tube closed (underpressure - because you don't have that T-connector) you could have problems (imho).
 

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The reason I thought it was for siphoning is that I saw once before where there were issues on a Kawasaki dirt bike that had siphon issues out the breather hose. It had no tee (stock) but added one and the problem was fixed. I also did a search and found it was Honda part #16958-GJ6-000. It is only used on California emission models in conjunction with the vapor canistor. The 49 state version does not use it and I would think if it were for air buffeting it would be needed in all states. The same part is used on many different Hondas including lawnmowers. If you Google that part number you should find lots of info. About the only thing I can't find is the purpose except for the following websites where members said it was to prevent siphoning.



Another reason I doubt it is because of buffeting is because I have a hydraulic and pneumatic background. One of the formulas are Force is equal to pressure times area. With only 5/16 or so diameter hole the force applied would be slight and then only if it were constant. Generally air passing by a tube will create vacuum. That is how you can siphon gas. Put a hose in the gas tank. Blow air across the open end and vacuum is created in the hose starting the siphon. That would be true only if there wasn't an open tee upstream of course. :ROFL: :ROFL:




http://www.vtxoa.com/forums/showthread.php?300019-Tank-vent-t




http://www.vtxcafe.com/showthread.php?t=8947
 

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Wijlle,

Well, I think we beat this subject to death but some debate can be good. At my age anything that makes me think is good.

I think you are right. Under almost all conditions nothing but air would go through the line. I think the problem lyes in just the right conditions are met. Say the tank were full and you stopped suddenly or went down a steep hill. Fuel could start to flow out the vent and siphon then siphon. I think 99.9% of the time it is not needed. Obviously when you build thousands of bikes it needs to be engineered to meet all needs. You or I might never need it in our life time, but another rider might live in an area where it is required each time he fills the tank.



I found people online who had siphon issue out the fuel tank vent hose. Most of them were dirt bikers who would really be at steep angles but the solution some used was to add the tee. I guess when the day is done it really doesn't matter. Both theory say the tee is open. :waving:
 
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