Dual Fuel Tanks

[Heatseeker]

I'm a visual kinda person, anyone care to diagram these setups? I like the idea of a switch to use the rear tank as a reserve so I know when I'm using my last bit of fuel. Nice XFS, btw, how can you keep it so white?!

Thanks! I don't know I've only had it for a week and keep it under plastic wrap till the season starts...
I agree about the switch as a reserve/safety but I'm not crazy about having to open the hood out in the middle of the lake if it cuts or even worse in the ocean...

 

[Heatseeker]

Nice ski! Congrats on the new purchase.

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Thanks! Cannot wait to ride!

 

[Heatseeker]

Am I thinking about this right? The smaller RRP should stay full until the Superjet tank is empty. At that point once the RRP is like half full, you will have to switch to reserve like normal. And I must be a marathon runner, bc I burn 6.5 gallons in the surf over 2-3 hours straight. Im getting a bit tired of carrying out a extra 2.5 gallon can on the front of the tray. That RRP rear tank is a awesome thing. I probably gotta make my own

Not sure this makes sense in my little brain... Would the pressure really transfer all the fuel? And I don't see why you would need a fuel switch or dual pick ups if they go to the same tank. Perhaps your diagram is correct but the RESERVE pick up would need to go into the SJ tank Vent. If pressure goes up due to RETURN, overflow into RRP through what you labelled SUPPLY. Once RRP empty, switch to reserve. Or, run ON to the SJ and the return into the RRP Vent and open the vent in the SJ so the RRP would be full until you switch, with overflow into the SJ. Once SJ is empty, Reserve is drawing from RRP and return into RRP leaving no unused fuel in the other tank and emptying SJ first. The pressure in the RRP may even prime the RESERVE line.

This is what it would look like:





Btw, what are you running to get 2-3 hours in the surf from 6.5 gallons? I can do about 2 hours on my stock superjet which holds a 1/4 gallon less fuel.

 

[Vumad]

Thanks! I don't know I've only had it for a week and keep it under plastic wrap till the season starts...
I agree about the switch as a reserve/safety but I'm not crazy about having to open the hood out in the middle of the lake if it cuts or even worse in the ocean...

You could run 2 petcocks. When you switch the fuel pickup petcock to reserve (RRP), switch the fuel return petcock to reserve (RRP) as well.

I've never tried the proposed vent setup, but I do know that if I remove a fuel line on a hot day before I open the gas cap, fuel goes everywhere. You will have to make sure your vent and tank does hold pressure though. A ski can run with no pressure in the tank, but that system wont work if something is keeping the pressure down.

 

[Heatseeker]

You could run 2 petcocks. When you switch the fuel pickup petcock to reserve (RRP), switch the fuel return petcock to reserve (RRP) as well.

I've never tried the proposed vent setup, but I do know that if I remove a fuel line on a hot day before I open the gas cap, fuel goes everywhere. You will have to make sure your vent and tank does hold pressure though. A ski can run with no pressure in the tank, but that system wont work if something is keeping the pressure down.

I don't want to reinvent the wheel or try something that may not be 100% and I'm starting to think the most practical would be to have a switch on the dash. Question is do I also need one for returns. If the two tanks can be connected in such a way that I didn't a switch at all that would be ideal for me. Hopefully someone can share a picture or diagram of a tried and true set up that works...

 

[speedysprocket]

I would take Curb's diagram and close the vent on the RRP and open the vent on the super jet tank. That way, as the carbs pull fuel, the void in the RRP tank is filled with fuel from the sj tank, not air from outside. And you'd probably want a one way valve to let air into the sj tank; not out. Otherwise, fuel might siphon from the RRP back into the sj tank... And get rid of the fuel selector switch- just more stuff to worry about and possibly break.
Carbs may need fine tuning based on how this system performs compared to a stock setup as well, but that's minor.

 

[SpaceCowboy]

Calling out TC Freeride and Gomez...how do you run dual tanks?


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[yamanube]

Pickup/out line from one tank into an inlet on the other, out from that one into fuel pump. Plug the vent on the second one. No switching.

 

[Balduccimoto]

Not sure this makes sense in my little brain... Would the pressure really transfer all the fuel? And I don't see why you would need a fuel switch or dual pick ups if they go to the same tank. Perhaps your diagram is correct but the RESERVE pick up would need to go into the SJ tank Vent. If pressure goes up due to RETURN, overflow into RRP through what you labelled SUPPLY. Once RRP empty, switch to reserve. Or, run ON to the SJ and the return into the RRP Vent and open the vent in the SJ so the RRP would be full until you switch, with overflow into the SJ. Once SJ is empty, Reserve is drawing from RRP and return into RRP leaving no unused fuel in the other tank and emptying SJ first. The pressure in the RRP may even prime the RESERVE line.

This is what it would look like:

View attachment 246384



Btw, what are you running to get 2-3 hours in the surf from 6.5 gallons? I can do about 2 hours on my stock superjet which holds a 1/4 gallon less fuel.

Yes pressure will really transfer all the fuel. It's actually how I syphon the gas out of my ski before yanking the tank out. Pressure actually is apart of the formula for fuel delivery. If you have the vent blocked off your tank then pressure builds up until it pops the needle off the seat in the carb and floods the engine. Thats what the vent is there for, and should pop off at maybe 6 psi. Some people who run a low pop off in the carbs risk flooding the engine. When I syphon gas, I pump into the vent line with a bicycle pump while the fuel line is overboard into a gas can.

A fuel switch or dual pick ups is for a reserve function. It can be deleted in my diagram if desired.

Your diagram looks like it would work too.

I am running a carbon ROK with SXR engine/pipe/ported/190 psi head. Lightweight hull helps fuel consumption for sure. Superjet gas tank is only 5 gallon?

 

[623pwr]

I like to isolate tanks just in of contamination and it gives me a gauge of were I'm at on fuel. Just a redneck way of doing it, but it works.

You guys have some clever ideas. A lot smarter then my complicated set up. I'll have to give them a shot. It is nice just filling up one tank too, it gets annoying filling up two tanks in the middle of the day, a lot lighter too.

 

[Heatseeker]

Yes pressure will really transfer all the fuel. It's actually how I syphon the gas out of my ski before yanking the tank out. Pressure actually is apart of the formula for fuel delivery. If you have the vent blocked off your tank then pressure builds up until it pops the needle off the seat in the carb and floods the engine. Thats what the vent is there for, and should pop off at maybe 6 psi. Some people who run a low pop off in the carbs risk flooding the engine. When I syphon gas, I pump into the vent line with a bicycle pump while the fuel line is overboard into a gas can.

A fuel switch or dual pick ups is for a reserve function. It can be deleted in my diagram if desired.

Your diagram looks like it would work too.

I am running a carbon ROK with SXR engine/pipe/ported/190 psi head. Lightweight hull helps fuel consumption for sure. Superjet gas tank is only 5 gallon?

Will need to mull this over a little longer I guess. I have a few weeks until the ice melts...

Superjet is 6.25 gallons: 4.8 + 1.45 reserve

 

[speedysprocket]

My superjet tanks maybe holds 5 gallons. Octane tanks hold like an extra quart. No way is a stock superjet tank 6.25 gallons.

 

[Heatseeker]

My bad 4.8 includes reserve of 1.45

 

[Heatseeker]

Got some info from Taylor Curtis who was really nice to help me out and I wanted to share in case this could also be helpful for others. This is how I will be setting it up but if you have 2 carbs, you also need 2 pick ups from front tank to back tank.

 

[kswiatk]

Out of curiosity, couldn't you have setup like this for the oil tanks on 650 and 750 kawi's? Just stick the oil tank in the original spot with the bottom line going to the vent of the main tank and then making a hole and attachment for a vent line and return line to the oil tank ? Only adds 3 quarts though.

 

[yamanube]

Out of curiosity, couldn't you have setup like this for the oil tanks on 650 and 750 kawi's? Just stick the oil tank in the original spot with the bottom line going to the vent of the main tank and then making a hole and attachment for a vent line and return line to the oil tank ? Only adds 3 quarts though.

Technically, you can do this with a second fuel tank, or an oil tank, or a milk carton, or a soda bottle, or a tupperware container, or a sippy cup, or a colostomy bag, or a party ball, or a booze bottle, or a water bottle, or a juice container, or a baby bottle, or a camel back. There are probably some other sort of containers I am missing and the aforementioned items may have varying degrees of success with fuel but you can likely get any of them to work.

 

[kswiatk]

Technically, you can do this with a second fuel tank, or an oil tank, or a milk carton, or a soda bottle, or a tupperware container, or a sippy cup, or a colostomy bag, or a party ball, or a booze bottle, or a water bottle, or a juice container, or a baby bottle, or a camel back. There are probably some other sort of containers I am missing and the aforementioned items may have varying degrees of success with fuel but you can likely get any of them to work.

Sweet. i got my new setup installed

 

[amitchell]

Sweet. i got my new setup installed View attachment 247826

Make sure to vent your bilge before you fire it up.

 

[whitca]

Sweet. i got my new setup installed View attachment 247826

Jeeez...all that engine bay porn and you go and c*ck it up with a screwdriver pole holder...wtf man. Clean it up noob

 

[DrGonzo]

Any updates. I just found a deal on an rrp rear tank and wanted to run both. Are you guys still running 2 tanks? Which setup did you go with?