I have a 84 fj1100. I was thinking of fabricating an underseat fuel tank. Think of it as a long term fix because our fuel tanks are not getting any younger. Sure I can use a fuel tank liner but I see this more as a "permanent fix". relocating the wiring and other stuff wouldn't be much of a problem. Now the question is what kind of fuel pump should I use? What should I install to stop the continuous fuel pump? Any help would be much appreciated as I don't have in depth knowledge as to converting our fj1100.
Change your float needle seats: http://rpmracingca.com/proddetail.asp?prod=3CF-14107-15 (http://rpmracingca.com/proddetail.asp?prod=3CF-14107-15)
Get a Yamaha fuel pump: http://rpmracingca.com/proddetail.asp?prod=YamFPump (http://rpmracingca.com/proddetail.asp?prod=YamFPump)
Get a fuel pump controller: https://www.ebay.com/itm/12v-Electric-Fuel-Pump-Relay-On-Off-Controller-Safety-Switch-3-Sec-Key-On-Primer-/332246190246 (https://www.ebay.com/itm/12v-Electric-Fuel-Pump-Relay-On-Off-Controller-Safety-Switch-3-Sec-Key-On-Primer-/332246190246)
Have you done a volume calc? 231 cubic inches per gallon so if you want 5 gallons you will need 1155 cubic inches of tank volume.
I'm not sure you have that kind of space down there.
I would love to see what you come up with.
If worried about the fuel tank integrity I recommend Caswell tank liner. That stuff is by far the best stuff on the market. I dumped the excess out a CB400F tank I lined onto my gravel driveway.... :Facepalm:
The Midget (Mike Ramos) has significant experience with an auxiliary tank. I believe it was a soft temporary tank, however, but I bet he can tell you some things.
Quote from: Pat Conlon on September 29, 2019, 10:11:15 AM
Change your float needle seats: http://rpmracingca.com/proddetail.asp?prod=3CF-14107-15 (http://rpmracingca.com/proddetail.asp?prod=3CF-14107-15)
Get a Yamaha fuel pump: http://rpmracingca.com/proddetail.asp?prod=YamFPump (http://rpmracingca.com/proddetail.asp?prod=YamFPump)
Get a fuel pump controller: https://www.ebay.com/itm/12v-Electric-Fuel-Pump-Relay-On-Off-Controller-Safety-Switch-3-Sec-Key-On-Primer-/332246190246 (https://www.ebay.com/itm/12v-Electric-Fuel-Pump-Relay-On-Off-Controller-Safety-Switch-3-Sec-Key-On-Primer-/332246190246)
Have you done a volume calc? 231 cubic inches per gallon so if you want 5 gallons you will need 1155 cubic inches of tank volume.
I'm not sure you have that kind of space down there.
I would love to see what you come up with.
(http://fjowners.com/gallery/11/1156_29_09_19_9_48_47.png)
Thank you for the reply. I was thinking of fabricating something similar to the picture I do have the space as I am currently not using the stock airbox
I'll also have to fabricate abattery box after the carbs. I will do the measurements to the rear subframe. Hopefully something around the 15L range.
Can a lithium battery work on it's side?
If so, put the battery on its side in your rear cowl...all that room you will now have :good2:
Maybe you could cut the bottom of the old tank out mount your new tank where the original tank was and use the top of the old tank as a cover for it.
Quote from: Pat Conlon on September 30, 2019, 01:08:40 AM
Can a lithium battery work on it's side?
If so, put the battery on its side in your rear cowl...all that room you will now have :good2:
I have the Lithium Batteries that Are sold through RPM. Their add does say that the battery can be used in any position.
https://www.firepowerparts.com/product/featherweight-lithium-battery/50983 (https://www.firepowerparts.com/product/featherweight-lithium-battery/50983)
Fred
Quote from: T Legg on September 30, 2019, 01:24:26 AM
Maybe you could cut the bottom of the old tank out mount your new tank where the original tank was and use the top of the old tank as a cover for it.
I have had the same idea but take it one step further, a solution for everyone as the need for tank replacements is only going to increase over time.
Get a plastic tank made to the FJ shape (we need someone in the business) and then, as you say, cut the bottom out of the original and use the top as a decorative cover / shell.
Noel
Quote from: T Legg on September 30, 2019, 01:24:26 AM
Maybe you could cut the bottom of the old tank out mount your new tank where the original tank was and use the top of the old tank as a cover for it.
That's what I was going to do. Maybe make a carbon fiber cover from the old tank. One of the many projects that got put on hold. When I started building my shop/house
anyone here who has an experience using mechanical or vacuum fuel pumps? I think it simplifies the process .
I wonder if a plastic tank will survive siting atop of an air cooled engine at the top end of temps sitting in traffic. Not all plastic like products are thermo-formed so I guess it can be done.
Mark, wouldn't it have to be a thermo-set plastic?
I like the carbon fiber idea but instead of a fake tank inside the original shell, make a carbon fiber duplicate of the original tank. Now that would be cool.
Joe
My XL 250 has a plastic tank as do many dirt bikes with giant desert tanks.they may not get as hot as an fj though but having a tank full of gas would keep the plastic cool.you could have a metal pan support the plastic tank so no plastic mounting tabs would deform from the heat.
Joe, yes, it would not need to be a thermo-formed plastic. But many fuel tanks are rotation formed (Roto-mold) and are a thermo-formed plastic. Other methods will just cost more due to the added labor and materials. Not saying it can't be done, just that the price might be above what one is willing to pay. The concept is perfect for replacing the rusting steel tanks on our aging loved ones.
Travis, the fuel thank with a volume of fuel would have a cooling effect till it is no longer filled. And you might have to agree that some FJ owners love to ride them till the last (maybe only) gas stop on the route.
Quote from: Tuned forks on September 30, 2019, 10:13:38 PM
Mark, wouldn't it have to be a thermo-set plastic?
I like the carbon fiber idea but instead of a fake tank inside the original shell, make a carbon fiber duplicate of the original tank. Now that would be cool.
Joe
Hey Joe, a couple of the FJ Racers over here used underseat fuel tanks and cut up their tanks and that they just used the top of the tank shell as a cover to make the bikes look "normal". Their idea was to take all that weight from above the engine and put it lower and to let the heat escape more quickly from the engine through big holes cut in the shell - but at the same time, they could only fit enough fuel in their tanks to cover 1 short race (about 7-8 litres) - you can't fit 22 litres under the seat without some serious fabrication and component moving !
Not a great picture but I hope you get the drift
(http://fjowners.com/gallery/11/6213_30_09_19_10_33_24.jpeg)
Filling the tank
(http://fjowners.com/gallery/11/6213_30_09_19_11_11_23_1.jpeg)
I was going to make a Carbon Kevlar shell from the original tank. And an aluminum tank underneath.
But like I said all projects on hold until I get the shop/house done.
Quote from: Millietant on October 01, 2019, 12:20:05 AM
Filling the tank
(http://fjowners.com/gallery/11/6213_30_09_19_11_11_23_1.jpeg)
this is very nice. do you have more pictures?
Quote from: T Legg on September 30, 2019, 10:34:35 PM
...... having a tank full of gas would keep the plastic cool......
I see several references to this. What keeps the fuel cool?
Having a full tank of fuel sitting on top of that motor when it's hot is no different to a pot of water over a fire. I'm not theorising here, if wearing shorts in stinking heat and in traffic (as I often do), I can't touch the tank with my inner leg, it's so hot it stings and I suspect if I left it there it might even burn, certainly feels like it would.
Noel
Quote from: fjman on October 01, 2019, 02:51:40 AM
Quote from: Millietant on October 01, 2019, 12:20:05 AM
Filling the tank
(http://fjowners.com/gallery/11/6213_30_09_19_11_11_23_1.jpeg)
this is very nice. do you have more pictures?
I'll see what I can find - will post some pics of the FJ's/racing on a separate thread.
Quote from: ribbert on October 01, 2019, 05:25:44 AM
Quote from: T Legg on September 30, 2019, 10:34:35 PM
...... having a tank full of gas would keep the plastic cool......
I see several references to this. What keeps the fuel cool?
Having a full tank of fuel sitting on top of that motor when it's hot is no different to a pot of water over a fire. I'm not theorising here, if wearing shorts in stinking heat and in traffic (as I often so),I can't touch the tank with my inner leg, it'ts so hot it stings and I suspect if I left it there it might even burn, certainly feels like it would.
Noel. The thought behind the fuel keeping the tank cool is that as it heats the evaporation causes cooling .With water it limits the temperature to 100 degrees Celsius untaill it boils away.water can absorb a great deal of heat .I don't know how gasoline compares in heat absorbing capacity but the effect is the same.I looked up the temperature that gas boils at and I saw a range of between 100 and 400 degrees Fahrenheit so the tank could still get pretty hot.
Quote from: ZOA NOM on September 29, 2019, 11:32:29 AM
The Midget (Mike Ramos) has significant experience with an auxiliary tank. I believe it was a soft temporary tank, however, but I bet he can tell you some things.
Gentlemen,
Another interesting discussion.
Not sure of how practical an under seat main tank would be as capacity for street use perhaps is a limiting factor. Below are some of the issues encountered when the location was considered.
The idea of fabricating an under seat auxiliary fuel tank was entertained. However for a variety of reasons the notion was set aside and a behind the rider location was proven more practical.
As Pat mentioned, 5 gallons of fuel is a considerable volume to squeeze into a limited space. The shape of the tank would have been "unique" to say the least.
Some of the options: The spring from the rear shock was removed to check total wheel travel & see if the front half of rear fender could be repositioned to allow additional room – proved not very practical.
The sides of the tank would be to the side covers – there was concern the air flow over the engine would be hindered – perhaps (perhaps gentlemen) one of the advantages of removing the stock air box & using pods is improved air flow over the engine as more air is allowed to escape from the rear – eliminating this possible advantage and then minimizing air flow to an even greater extent by filling in more space than the stock air box seemed detrimental.
As it is, since no consideration of damping the engine noise is of concern and in an effort improve the possible cooling effect, the insulation on the inner side panels has been removed (it was in a deteriorated condition anyway).
As experienced many times in hot weather the main tank gets extremely hot. An under seat would seem to have even more of a heating problem.
The lithium battery would have been mounted in the rear tail piece – but then the storage of the tool & patch kits & miscellaneous items would have been eliminated – they would have been placed in a tail pack which is not much of an advantage.
To maintain fuel level equilibrium in both the under seat tank and the main tank, either a long neck filler tube would have to be considered or the under seat tank would have had to be sealed in some way. Some type of venting would need to be employed. None of the options proved practical – at the very least, positive & redundant fuel shut off from both tanks would have to be assured which and such assurance is difficult to ascertain when the tank is buried & out of sight.
The solution settled on was an aluminum tank sized for a commonly available tail pack which should help protect the tank in case of a fall. Aluminum was chosen not for the weight savings (over steel) but because it will not spark in case of an accident. The total volume is 5.3 gallons (although 5 gallons is considered full).
There is an electric automotive two way fuel transfer valve installed – the normally open side is plumbed to the main tank so if it fails, the main tank can be used normally. In addition to the fuel transfer valve, for safety there is a redundant electric on/off valve between the auxiliary tank and the fuel transfer valve. Finally there is a mechanical Pingel valve on the tank itself within easy reach while under way.
Every switch is independently fused for added safety plus should the need arise, it is relatively easy to determine the cause.
The tank is directly behind the rider held in place with ROK straps. There is a quick disconnect fuel line which sets behind the right side cover. Installation & removal takes a minute.
Although the explanation seems involved, it is actually a quite simple & straight forward installation.
Ride safe,
Midget.