Kawasaki Concours Forum
The C-14, aka Kawasaki Concours-14, the new one :) => Accessories and modifications - C14/GTR 1400 => Topic started by: 4cedars on July 16, 2011, 06:39:55 PM
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Installed a 4 gallon aux tank in the location of the luggage rack. I used 3/8 hose and fittings down to the bulkhead fitting at the bottom of the main tank. There is a vent line with a 3/8 hose on the aux tank and yes it is clear :-). While riding the tank will gravity flow so slow the fuel guage will not move for 25 miles. Yet when I stop and pop the cap the entire tank will empty in 3 minutes. Going for some Q tomorrow, starting with a full aux tank and 1/2 main tank. It will be 160 mile round trip, going to turn on the valve when I leave and see what happens. If anybody has any experience with this or suggestions I would appreciate it. I really dont want to install a in-line pump but I am tired of pissing with this and need to get to installing the Rostra I just got from Murphs. John
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If the fuel will flow properly by just loosening the cap it's a venting issue. Basically the aux tank is trying to flow fuel to the main tank, but at the same time is trying to pull air from the main tank back to the aux tank to alleviate a vacuum in the aux tank. What type of aux tank is it and how is it vented?
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Its a JAZ tank with the vent tube out the top of the tank and the outlet on the lower. The puzzling thing is that when I pop the cap on the main tank there is a vacuum inside so why does the fuel not flow from the aux tank if there is negative pressure in the main tank. Before opening the fuel cap on the main I am unable to blow air into the aux tank but once I pop the cap on the main I am able to blow air into the aux tank
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It is a vent problem but it is the main fuel tank, not the aux. tank. The main fuel tank has a spring and a plunger in the exhaust circuit to resist venting a little bit, not enough to damage the tank but apparently enough to defeat you in trying to fill the main tank with such a small amount of differential pressure (very little, maybe .3 PSI). I can think of only three solutions: 1) add a vent between the main tank and the aux. tank, making sure the vent enters the tank on both ends above the level of each tank when it is full. Of course this is a lot of work and subject to leaks, etc. 2) As you mention, add a pump to increase the pressure differential to make the main tank vent when being filled from the aux. tank. This is probably the most elegant solution and other than cost, the only real effort is in the wiring I believe. 3) Open the main fuel tank cap when transferring fuel between tanks. This has the very obvious problem that it won't work if you have a tank bag, and it is a bad idea to do this when it is raining out. Of course you really don't have to swing the cap wide open, just barely crack it open so the tank vents to atmosphere.
You could also add a vent to the main tank that is always open but I think that is a bad idea for several reasons including the likely venting of fuel occasionally.
Your description of blowing into the vent of the aux. tank conjures up mental images for me and I am having trouble whisking them away. I hope you did this in a closed garage and not in the driveway, during daylight hours, or the neighbors may talk quietly between themselves and point at you when they see you, at least for a while. ;D ;D
Brian
Its a JAZ tank with the vent tube out the top of the tank and the outlet on the lower. The puzzling thing is that when I pop the cap on the main tank there is a vacuum inside so why does the fuel not flow from the aux tank if there is negative pressure in the main tank. Before opening the fuel cap on the main I am unable to blow air into the aux tank but once I pop the cap on the main I am able to blow air into the aux tank
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Brian, I was hoping you would see this post and respond. I figured you would have the answer to the problem. Looks like I will just add a 35 dollar universal in line pump. So much for all the AN8 fittings and 3/8 hose hoping for a low restriction system :banghead:
And yes the garage door was shut during my Scientific Wilda.. Experimentation. But had it not been, the family and neighbors would have understood, since they accuse me of having an "odd" attachment to my "baby". I'm sure others here can understand and sympathize ;)
In all seriousness thanks for your input, I greatly appreciate it. John
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Might want to look at the stock fuel cap before investing in a fuel pump. On my old Road Star it was a common problem for tanks in the southwest to bulge due to pressure build-up when the gas vapors in the tank would expand on hot days (even with vent in the filler neck). Also, a similar issue to yours was experienced when upgrading from the stock 40mm CVS carb to a 42 or 45mm HSR carb. The solution was to disassemble the stock fuel cap and remove the rubber plugs from the factory vents. Here's an article with pic's to give you a better idea of what I'm talking about.
http://roadstarclinic.com/content/view/136/96/ (http://roadstarclinic.com/content/view/136/96/)
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I actually had a fuel cap apart off my C-14 after it started leaking and I will say.... what a gizmo! More parts in there than you can shake a stick at. A plumbing work of art. I even took some photos because I really could not believe how many parts were in there:
Look how many parts are in the fuel cap:
(http://i45.photobucket.com/albums/f82/BDF08012008/fuelcapparts2.jpg)
Even Kirby could not believe it!
(http://i45.photobucket.com/albums/f82/BDF08012008/Kirbyputoff.jpg)
This is one part of the venting system:
(http://i45.photobucket.com/albums/f82/BDF08012008/Pressureventgroup.jpg)
This is the vacuum side, the brass slug provides the resistance to the vent opening with sheer weight:
(http://i45.photobucket.com/albums/f82/BDF08012008/Vacuumvent.jpg)
The potmetal housing that contains all the small parts:
(http://i45.photobucket.com/albums/f82/BDF08012008/Insidefuelcap.jpg)
The back of the cap with the scroll venting assembly (the rubber part fits into the well in the metal casting):
(http://i45.photobucket.com/albums/f82/BDF08012008/Undersideofcapandseal.jpg)
I am looking at aux. tanks also so please tell me where you found a $35 external fuel pump? The least expensive pump I have found was an Airtex at Summit for something like $60 or so.
Brian
Brian, I was hoping you would see this post and respond. I figured you would have the answer to the problem. Looks like I will just add a 35 dollar universal in line pump. So much for all the AN8 fittings and 3/8 hose hoping for a low restriction system :banghead:
And yes the garage door was shut during my Scientific Wilda.. Experimentation. But had it not been, the family and neighbors would have understood, since they accuse me of having an "odd" attachment to my "baby". I'm sure others here can understand and sympathize ;)
In all seriousness thanks for your input, I greatly appreciate it. John
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Agreed that that will work as a solution to fill the main tank from the aux. tank. I believe the reason the venting restrictions are in the tank to begin with are to reduce the amount of fuel thrown overboard due to sloshing, especially when the fuel tank is full or nearly so. ??
It is fairly easy to do try though; I believe the brass plunger, shown in my photos, is the part that would have to be removed to make the vent free- flowing. Just a suggestion but be careful when taking the fuel cap apart- there are a lot of small parts, including springs, that will fall out and make reassembling it difficult, especially trying to determine the order in which the parts originally fell out.
Brian
Might want to look at the stock fuel cap before investing in a fuel pump. On my old Road Star it was a common problem for tanks in the southwest to bulge due to pressure build-up when the gas vapors in the tank would expand on hot days (even with vent in the filler neck). Also, a similar issue to yours was experienced when upgrading from the stock 40mm CVS carb to a 42 or 45mm HSR carb. The solution was to disassemble the stock fuel cap and remove the rubber plugs from the factory vents. Here's an article with pic's to give you a better idea of what I'm talking about.
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http://www.jegs.com/i/Mr.+Gasket/720/42S/10002/-1 (http://www.jegs.com/i/Mr.+Gasket/720/42S/10002/-1)
Here ya go it is 38 not 35 though
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Brian, I am told that pumps similar to that one is available at local farm stores also. We have Farm and Fleets where I am. My cousin picked his up there for his GL1800 aux tank. John
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http://www.carshopinc.com/product_info.php/products_id/72056/210-504-03 (http://www.carshopinc.com/product_info.php/products_id/72056/210-504-03)
MrFurious here is the tank I am using, John
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I have a feeling that an aux tank, sitting on the back rack, high above the top of the main tank, in this manner will overfill the main if you mess with the venting on the main. You will end up puking gas out the overflow.....not good. (liquids seek an even level...)
My pal Roger ran an aux tank on the C14 in the Ironbutt 2009, and I believe he had an inline shutoff for this exact reason, as he was puking fuel out the overflow because he messed with the vents. I'll ask him what his final solution was, and get back to you.
Adding a pump to force fuel from B to A will exascerbate an alredy potential problem....
I beleive Davo Jones also had this exact same dilemma, and used a manual shutoff, and only filled the main from the reserve when the level was low on the main, not running a closed system with both feeding constantly.
if you tied the main tanks vent, directly to the aux tanks vent, you would get a constant flow, but if you by chance opened the main tanks lid, it would erupt the full contents from the aux tank out of the main tanks cap in seconds.
so with the reserve sitting up there where it is, resign to the fact it can only be used to refill the main, by opening a shutoff valve with the main cap open. The main cap was never designed to resist the overpressure of pumping fuel into it above atmospheric pressure, with a head height above the filler neck. A bit more thought prior to the expense laid out would have made this all clear, sorry to be the bearer of sad tidings.
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MOB, I am also running an inline shut off and was planning on only dumping the load of fuel when the level in the main tank was low enough to accept the entire load. So the aux tank was either full or empty so as not to have any ill handling effects from a partial load moving around even though there is foam in the tank. Thanks for jumping in here, anything you find out from your friend would be appreciated, John
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Went for Q today and when the fuel gauge got down to 1 bar I used the fob key and popped the fuel cap to vent the main tank. The entire load from the aux tank emptied within 7 miles. The valve was on during the first 40 miles of the run and the gauge only moved down. I thought maybe it would at least draw from the aux tank and the level would stay at or close to constant, but it did not.
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That makes perfect sense if you put the aux. tank on the luggage rack; the entire aux. tank is above the top of the main fuel tank. It works out great that the main tank holds the entire aux. tank even before the main tank is empty too.
What you did today will work forever, it is just a tad clunky. If you are careful though, you should even be able to refuel the main tank in the rain, at least at speed, because there is very little water on the tank unless you are in a downpour. The fuel pump is a nicer solution but will take more money and more work to install it.
Another thing I would question about an electric pump is whether or not it can be run dry. If not, it is going to be tough to know when the aux. is empty and the pump is trying to pump air. You can get a good idea of how long the pump has to run but time alone won't be an exact measure under different circumstances (temperature, how much fuel in the main tank to start, etc.).
Brian
Went for Q today and when the fuel gauge got down to 1 bar I used the fob key and popped the fuel cap to vent the main tank. The entire load from the aux tank emptied within 7 miles. The valve was on during the first 40 miles of the run and the gauge only moved down. I thought maybe it would at least draw from the aux tank and the level would stay at or close to constant, but it did not.
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Brian, I dont plan to continue this way it was just an experiment for fact finding. While riding ,was thinking may something like a valve on the front of the tank to admit air. I kept thinking about something similar to a pressure relief valve or bleed valve on a compressor or a rollover valve in reverse. Just ideas, I really dont know what is available for an application such as this. I run with a tank bag so popping the cap really is not an option. On another forum it was suggested that I install a compression type fitting with a piece of brake line going into the tank down low near the bulkhead fitting up to the opening and plumbing a flexible line from the tank to the vent on the aux tank. What are your thoughts on this. I really do not want a pump on the connie only as a last resort. John
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the easist, and most viable, yet still dangerous solution, is to run a bulkhead(thru) fitting from the bottom of the tank with a tubular vent line, up, and internal within the main tank, to a "full" point just under the filler cap, with the other end external of the tank, with an inline shutoff also, and the tube end sitting well above the filler cap, or internal tube end. opening the valve on the vent line will permit the flow to the main tank because you are allowing air to escape, and fuel to flow in, but still require you to shut off the valve when fuel comes spewing out of the vent.... a messy proposition at the least.
as I noted, there is no simple and easy/cost effective systematic installation to couple these 2 tanks, with one sitting well above the other, in a closed loop assembly.
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Yes, venting the main tank will work. If I understand what you are suggesting, you are saying to put a fitting in the bottom of the tank and then run something (tubing?) up from that fitting to the top of the tank: yes, that should work fine. If you tie the new main tank vent to the aux. tank, then even if that internal tube should fail in any way, the system won't vent fuel overboard, it simply won't fill very fast and that will alert you to the problem.
Actually a system like that will even help prevent the main tank from ever overfilling, at least very fast. Once the main tank is full to the vent you install, the whole process of transferring fuel will either stop outright or continue but very slowly.
As I think about it, that is a great idea really. Your ideas for internal tubing are good but any long tube attached at only one end is subject to failure as time goes by; it would really help the situation if you could anchor the other end (top) of that tube to the fuel tank somehow. Maybe some type of clip that attaches to the filler neck spout? Like a band wrapped around the filler neck with a protruding piece on the side to hold the end of the tube in place. You can also use a piece of rigid tubing if you mount both ends and done reasonably well, that whole thing should out-last the bike itself I think.
Not having thought about this too much, I would say a second vent line tied to both tanks and a strictly gravity fed aux. tank would be the best way to go. No electrics to fail, no wiring, no additional plumbing in the fuel line that could leak, and no vibration from a pump that also may cause leaks.
Physics is your friend.... sometimes. ;) And it seems to be so in this case. I would like to have an aux. tank a bit lower on the bike and that just won't work without a pump.
Brian
Brian, I dont plan to continue this way it was just an experiment for fact finding. While riding ,was thinking may something like a valve on the front of the tank to admit air. I kept thinking about something similar to a pressure relief valve or bleed valve on a compressor or a rollover valve in reverse. Just ideas, I really dont know what is available for an application such as this. I run with a tank bag so popping the cap really is not an option. On another forum it was suggested that I install a compression type fitting with a piece of brake line going into the tank down low near the bulkhead fitting up to the opening and plumbing a flexible line from the tank to the vent on the aux tank. What are your thoughts on this. I really do not want a pump on the connie only as a last resort. John
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Thats what I was thinking, if the valve got opened to early to dump the load the internal vent would be covered with fuel and with it tied to the aux tank vent it would cause the same situation that I am trying to remedy right now. I could not imagine that the gravity fed fuel coming into the tank would push the fuel uphill back to the aux tank and continue to fill the main tank. In fact now that I am thinking/writing it, if fuel got into that "return" vent line it may cause another problem.
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Here's the problem - the engine sits under the main fuel tank and pressurizes it more than an aux tank mounted someplace else.
Personally, what I would do is this:
1. Install an aux tank with a fuel cap vented in a similar fashion to the main tank, so it allows for a slight pressurization.
2. Install a "Y" fuel fitting with a switchover valve, so you can select one tank or the other. Just like on an aircraft. In fact, you could probably USE an aircraft switchover valve. I'd opt for a Piper, which is right/left/off vs. a Cessna which is right/left/both/off. I don't think you would want to use both or you couldn't manage fuel burn between the tanks.
3. Run the aux down first so you have the benefit of the fuel gauge on the main tank after switching. If that's important. I'd just use one trip odometer for the main and the other for the aux.
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I don't think the vent line willing with gasoline would be a problem- gasoline is very thin and has virtually no surface tension so it will not cling or clog in a tube like water would. I think it would clear itself as soon as the level in the main tank dropped enough to clear the end of the vent tube. And even if it did not, as the level dropped in the main tank the differential pressure would increase (due to the increasing difference between the two tank's levels) until the vent line did clear. At least that is how I believe it would work but I would have to test it to verify that.
Still, if you just wait until the main tank is low enough to accept the full volume from the secondary tank, the vent line idea will work very well.
The last thing you could try would be to just see if the aux. tank will flow enough fuel into the main tank to drain the aux. tank with the bike running and the main fuel tank cap closed. You said it fills very slowly like that but the bike uses fuel very slowly too so it might work out OK if you wait until, say, the main tank was 1/2 empty and open the transfer line valve. The very worst thing it could do was simply to not work fast enough and cracking the cap on the main tank will always fix that.
I do not think that fuel sloshing will be a problem with foam in the aux. tank even when it is around ½ full. There is no real side- to- side force generated when riding a motorcycle anyway and a bit of fore- aft sloshing will not be a problem. As riders sitting relatively unattached on top of motorcycles, we tend to ‘slosh’ fore and aft ourselves due to acceleration and braking anyway. :D
Brian
Thats what I was thinking, if the valve got opened to early to dump the load the internal vent would be covered with fuel and with it tied to the aux tank vent it would cause the same situation that I am trying to remedy right now. I could not imagine that the gravity fed fuel coming into the tank would push the fuel uphill back to the aux tank and continue to fill the main tank. In fact now that I am thinking/writing it, if fuel got into that "return" vent line it may cause another problem.
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I am going to stop at FASTENAL and see what is available for the vent tube in the tank. If I remember when I pulled the pump to install the bulkhead fitting there were small tubes inside the tank from the factory. I may be able to secure my vent tube alongside those. I cant remember exactly how they ran I just remember seeing them. The engine uses fuel faster than the aux tank will replenish it in the current form, as I figured out yesterday. John
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That is a great idea- attach your new vent tube to one of the vent tubes already brazed into the tank. Both vent lines go from the extreme back of the tank (where the rubber tubes connect, under the saddle) to the area immediately around the filler cap (or as it is humorously known around here, courtesy of Haroldo, 'gashole').
Brian
I am going to stop at FASTENAL and see what is available for the vent tube in the tank. If I remember when I pulled the pump to install the bulkhead fitting there were small tubes inside the tank from the factory. I may be able to secure my vent tube alongside those. I cant remember exactly how they ran I just remember seeing them. The engine uses fuel faster than the aux tank will replenish it in the current form, as I figured out yesterday. John
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Thanks for being a sounding board on this Brian, it is appreciated. John
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Glad to be of any help that I can John. Hope it works out for you. I have gotten some excellent information and ideas from this forum so I try to give a bit back where I can.
I am thinking about doing something similar and so was already thinking about the whole fuel transfer problem.
Brian
Thanks for being a sounding board on this Brian, it is appreciated. John