Aux tank installation 2018 GSA
- Thread starter redwinger
- Start date
Yes a few changes I'm making. First I didn't go under the main tank and up to follow the stock vent line so I'm doing that as I think I had too many sharp bends and a 1/4" line is easy to kink.
Second I'm going to vent not to the back of the bike but to the bikes stock charcoal cannister again to ensure no chance of clogging.
I didn't remove that ball bearing, I'll do that this time.
And third I'm going to skip the fuel filter.
For the ibr I ran a small 2.5 gallon aux tank but I just ordered a 5 gallon so I'll make my changes when the new tank comes.
Second I'm going to vent not to the back of the bike but to the bikes stock charcoal cannister again to ensure no chance of clogging.
I didn't remove that ball bearing, I'll do that this time.
And third I'm going to skip the fuel filter.
For the ibr I ran a small 2.5 gallon aux tank but I just ordered a 5 gallon so I'll make my changes when the new tank comes.
I'm giving it another go with a 5.2 gallon tank I just installed on my plate, my IBR tank was too small. I picked up extra rigid premium marine fuel line, almost impossible to collapse or kink and will be removing the ball bearing too. Going to give it a good test run during the Void and Butt Lite. Could have gone a little bigger but 10.5 gallons at 40-45 mpg is enough for me.
I have just done this to my 2013 model using a vacuum assisted feed through the vent line. Took it out for a 3000k shake down run on the weekend. Worked fine untill something blocked the fuel line at the vent spigot. This is the smallest diameter opening in the system not much more than 3 mill at the seat for the roll over valve. You may want to reconsider the inline fuel filter. I was surprised at the level of vacuum this caused in the main tank tank and mine is the old style plastic job. So very robust. The reduction in fuel flow from the Aux also allowed pressure to build in that tank in the heat as well. Not good all round and had to pull it apart mid run to get the main tank to vent properly again.
I will be putting a fuel filter in the line this weekend.
Just a heads up
I will be putting a fuel filter in the line this weekend.
Just a heads up
Wonder if anyone thinks this is a good or bad idea; since the main bike tank now vents through the aux tank and since the aux tank only has a 1/4" vent hose that can be easily clogged I was thinking of adding an adapter from the aux tank nipple that increases the line size from 1/4" to 1/2" or so to provide a larger hose to vent from.
My idea is that it would have a lower amount of vac when venting, may suck in less debris and if it did, less likely to clog compared to a 1/4" line.
Over thinking it or brilliant idea?
My idea is that it would have a lower amount of vac when venting, may suck in less debris and if it did, less likely to clog compared to a 1/4" line.
Over thinking it or brilliant idea?
Again, my tank is installed the same way as yours. My tank was designed by Ernie Azevedo and he felt my tank needed more venting when operating in this configuration (he had the same tank on the same bike). He put a second hole at the top of the fill neck (the first hole was for the vent line) and put a wire mesh vent plug into that hole as a solution (picture of plug below). For the IBR, I didn't want to deal with Warchild if he was having a bad day 
, whereby I would have to engineer an alternate solution in a hot parking lot, so I asked Ernie about plugging that hole and he was pretty emphatic that the system needed the extra venting. I ended up replacing the vent plug with another length of 1/4" fuel line and routed it down with the other one--so essentially I have two identical 1/4" vent lines coming off the filler neck. At some point I will replace the vent plug and remove one of the vent lines.
Bottom line: I've had twice the venting for two IBRs now and haven't had any issues. I can't prove a negative, so have no idea if it would have been bad to not have the second vent line.
, whereby I would have to engineer an alternate solution in a hot parking lot, so I asked Ernie about plugging that hole and he was pretty emphatic that the system needed the extra venting. I ended up replacing the vent plug with another length of 1/4" fuel line and routed it down with the other one--so essentially I have two identical 1/4" vent lines coming off the filler neck. At some point I will replace the vent plug and remove one of the vent lines. Bottom line: I've had twice the venting for two IBRs now and haven't had any issues. I can't prove a negative, so have no idea if it would have been bad to not have the second vent line.
I've seen multiple set ups like this, using the vent line to feed the main tank from the aux and the only venting being thru the aux tank. Yes, it works. But it often has issues during the ride and more often has issues than just doing a bulkhead fitting and running a larger line, gravity feed and allowing the normal main tank vent to exist with a standard vent/overflow line on the aux tank. Camel Tanks work this way. Ask Terry Lehman about the fun he had with his/Linda's Africa Twin using a Camel Tank during the IBR and also his recent fuel pump issue during the SBR. Sound familiar? It should. It's fine for a smaller displacement bike that's not seeing rally use.
IMHO, you're working way too hard to avoid doing it correctly in the proven manner. 1/4 lines don't transfer fuel very fast. Note to Marc B. - That slight rush sound is because you're using fuel faster than the line will allow transfer from the aux. You're not venting the main tank while you're pulling fuel from the aux at vacuum, and the inability of the line to handle the draw means additional vacuum in the main tank. This stresses the fuel pump too. You're just asking for a repeat fuel pump failure.
And not running a filter on the line from the Aux tank is just dumb. You're relying solely on the tea bag filter on the fuel pump then. And it's not like you're going to swap that out during the rally. Not to mention that a clear plastic fuel filter on the aux tank line is often a heads up that you got some bad gas at your last fill. (Cue to Greg Rice - Take the blue aluminum one off and put a clear plastic one on, and carry a spare.) Bling won't get you home.
Just IMHO gents. Drilling the tank isn't that hard. And it's a simple, proven method that works and rarely has issues. Bad line routing and venting issues can occur with any aux fuel set up. But running 5/16 lines makes it easier to route and flows enough gas to avoid many issues.
IMHO, you're working way too hard to avoid doing it correctly in the proven manner. 1/4 lines don't transfer fuel very fast. Note to Marc B. - That slight rush sound is because you're using fuel faster than the line will allow transfer from the aux. You're not venting the main tank while you're pulling fuel from the aux at vacuum, and the inability of the line to handle the draw means additional vacuum in the main tank. This stresses the fuel pump too. You're just asking for a repeat fuel pump failure.
And not running a filter on the line from the Aux tank is just dumb. You're relying solely on the tea bag filter on the fuel pump then. And it's not like you're going to swap that out during the rally. Not to mention that a clear plastic fuel filter on the aux tank line is often a heads up that you got some bad gas at your last fill. (Cue to Greg Rice - Take the blue aluminum one off and put a clear plastic one on, and carry a spare.) Bling won't get you home.
Just IMHO gents. Drilling the tank isn't that hard. And it's a simple, proven method that works and rarely has issues. Bad line routing and venting issues can occur with any aux fuel set up. But running 5/16 lines makes it easier to route and flows enough gas to avoid many issues.
Well I for one am giving up on the vent idea for connecting my aux tank. It worked great for a while, but recently I was getting negative pressure in the main tank. Evidenced by a rush of air when I opened the cap.
I ran a few tests and near as I can tell two areas seem to be causing the issue.
1. Flowing air from the fuel line from aux tank to main bike vent flows fine and easy, however over time I noticed fuel gathers in the low area of the fuel line, think like a trap in your sink drain. That fuel seems to not have enough suction to pull it up when there is air in the line as is when the aux tank is empty, so some air flows to the vent, but not enough to vent the main tank but enough to prevent the small fuel amount to from sitting in the line and restricting air flow.
2. If I blow air from tank vent through to the main tank with the cap open, it is very very difficult significantly so when compared to just blowing air directly in the fuel line disconnected from the aux tank.
This makes me believe, and I am sure there is some sort of scientific calculation here that the 1/4 inch output of the aux tank is insufficient to flow enough air at any capacity when compared to the line disconnected from the aux tank. Since air seems to flow easier than fluid I'm guessing this problem is exponential.
So, boiled all down before I burn out another fuel pump I pulled my aux tank and will pull the main tank and find a spot for a bulkhead fitting and either gravity or fuel pump feed it.
I know lots of people do the vent method without issues, but for me, something just doesn't seem right and once bitten, twice shy I suppose.
I ran a few tests and near as I can tell two areas seem to be causing the issue.
1. Flowing air from the fuel line from aux tank to main bike vent flows fine and easy, however over time I noticed fuel gathers in the low area of the fuel line, think like a trap in your sink drain. That fuel seems to not have enough suction to pull it up when there is air in the line as is when the aux tank is empty, so some air flows to the vent, but not enough to vent the main tank but enough to prevent the small fuel amount to from sitting in the line and restricting air flow.
2. If I blow air from tank vent through to the main tank with the cap open, it is very very difficult significantly so when compared to just blowing air directly in the fuel line disconnected from the aux tank.
This makes me believe, and I am sure there is some sort of scientific calculation here that the 1/4 inch output of the aux tank is insufficient to flow enough air at any capacity when compared to the line disconnected from the aux tank. Since air seems to flow easier than fluid I'm guessing this problem is exponential.
So, boiled all down before I burn out another fuel pump I pulled my aux tank and will pull the main tank and find a spot for a bulkhead fitting and either gravity or fuel pump feed it.
I know lots of people do the vent method without issues, but for me, something just doesn't seem right and once bitten, twice shy I suppose.
I wanted to add to this conversation as I did this same AUX tank plumbing on my new FJR and I wanted to see what EricV had to say.
I bought a new 2018 FJR A model a month and a half ago and I spent a little time looking into how the best way to plumb a AUX tank in to the main tank. I read all of the posts here and other places how to drill the main tank and install a bulkhead fitting. I have done that process on many motorcycles ( mostly gold wings ) since 2004 and I always found it unnerving when I drilled a hole in a perfectly good gas tank. So I looked at other options like I had done on my 2018 Gold Wing and my 2019 GSA which is to tap into the gas tank vent system to draw gas from a AUX tank. It worked well on the Gold Wing and the GSA so why not the FJR.
I did some research and found the FJR has the same closed loop fuel system like all modern motorcycles and in theory it should work on the FJR.
I found some photos of the gas tank online that showed two small tubes coming out of the bottom left side of the gas tank. I did some more research and found one is for the vent to the gas tank and the other is the rain water drain from around the gas cap.
I rode over to Joe Green's house as he has a nice motorcycle lift so we could take a better look and do some testing to confirm what I had read.
We removed the gas tank and found the two metal tubes like in the photos and there was a rubber tube running from each and there was a t valve where the two rubber tubes were merged into one. I found this interesting as one of the metal tubes is for the gas tank vent which sucks air up into the gas tank and the other is a water drain that allows water to run down into the tube and out under the bike.
To confirm which metal tube is the gas tank vent we used a air compressor to blow air into both metal tubes. Once we had that figured out I ran my AUX tank fuel line to the front metal tube and removed the T valve and connected the rubber drain tube to the back metal tube for the water drain.
I temporally mounted my smaller GAS AUX tank ( 3.4 gallons ) for testing. I removed the passenger seat and the AUX tank fit nicely in that spot.
The way this works is that as the engine pulls / pumps gas from the main tank it sucks air through the vent line. It is a very slow process. So instead of sucking air through the gas tank vent line it is now sucking gas. The AUX tank becomes the vent for the main gas tank.
So far I have ridden 500+ miles with this setup and filled the AUX tank 3 times ( I did not wait for the main tank to be empty ) and each time the AUX tank emptied be while the fuel gauge continued to show full.
I need more testing ( hopefully this coming weekend I will get to ride a couple thousand miles ) and I need to see how it works when it gets damn hot outside.
I bought a new 2018 FJR A model a month and a half ago and I spent a little time looking into how the best way to plumb a AUX tank in to the main tank. I read all of the posts here and other places how to drill the main tank and install a bulkhead fitting. I have done that process on many motorcycles ( mostly gold wings ) since 2004 and I always found it unnerving when I drilled a hole in a perfectly good gas tank. So I looked at other options like I had done on my 2018 Gold Wing and my 2019 GSA which is to tap into the gas tank vent system to draw gas from a AUX tank. It worked well on the Gold Wing and the GSA so why not the FJR.
I did some research and found the FJR has the same closed loop fuel system like all modern motorcycles and in theory it should work on the FJR.
I found some photos of the gas tank online that showed two small tubes coming out of the bottom left side of the gas tank. I did some more research and found one is for the vent to the gas tank and the other is the rain water drain from around the gas cap.
I rode over to Joe Green's house as he has a nice motorcycle lift so we could take a better look and do some testing to confirm what I had read.
We removed the gas tank and found the two metal tubes like in the photos and there was a rubber tube running from each and there was a t valve where the two rubber tubes were merged into one. I found this interesting as one of the metal tubes is for the gas tank vent which sucks air up into the gas tank and the other is a water drain that allows water to run down into the tube and out under the bike.
To confirm which metal tube is the gas tank vent we used a air compressor to blow air into both metal tubes. Once we had that figured out I ran my AUX tank fuel line to the front metal tube and removed the T valve and connected the rubber drain tube to the back metal tube for the water drain.
I temporally mounted my smaller GAS AUX tank ( 3.4 gallons ) for testing. I removed the passenger seat and the AUX tank fit nicely in that spot.
The way this works is that as the engine pulls / pumps gas from the main tank it sucks air through the vent line. It is a very slow process. So instead of sucking air through the gas tank vent line it is now sucking gas. The AUX tank becomes the vent for the main gas tank.
So far I have ridden 500+ miles with this setup and filled the AUX tank 3 times ( I did not wait for the main tank to be empty ) and each time the AUX tank emptied be while the fuel gauge continued to show full.
I need more testing ( hopefully this coming weekend I will get to ride a couple thousand miles ) and I need to see how it works when it gets damn hot outside.