Topic: Under Seat Fuel Tank

[Honda?]

So here's the deal. I have a fiberglass tracy body with the bottom of the tank cut out. (I did that with good reason) In order to make it work again it will need somewhere around 1000 dollars of work. Either for a fitted aluminum tank in the gas tank section or new epoxy resin set in and stuff.

My Question
Has anyone toyed with the idea of building a gas tank to fit where the oil tank, battery, and fuses go under the seat? Ya know...to lower the center of gravity.

On the same note could someone have a custom aluminum two chamber tank for gas and oil placed down there while moving a different shaped battery and the fuses to where the gas tank used to be?

What would have to be done to solve the fueling problem? Fuel pump to the carbs? <loaded question. 

On top of that in order to make more space for fuel or oil tank capacity you could route the air box(shaped to fit) under the gas tank section too.


Am I onto something or should I just check into the psych ward now?

[Honda?]

Also depending on how the tank is built there is a chance it could also be used as a frame support when it's bolted up.

Anybody know off of the top of their head what capacity the oil tank have to hold?

[bucky katt]

i would never consider using any tank as a structural member but least of all fuel. all it would take is a slight miscalculation of the forces on the tank for a crack to develop or a weld to go bad. i wouldnt think that theres enough space in that area to put much more than a 1 or 1.5 gallon tank anyways. just fix the tracy body, i dont think it will cost as much as you think to repair it, hell it's apart now, why not get a rubber fuel cell bladder to line the tank and then re-glass the underside. that way no fuel in contact with the fiberglass.

[seaweb11]

Sounds like time to scrap the Tracy for a bit if you want to ride and keep your sanity.

I'm sure you are watching this, http://cgi.ebay.com/ebaymotors/CB750-SOHC-CAFE-RACER-FIBERGLASS-RACE-FAIRING-TANK_W0QQcmdZViewItemQQhashZitem3a5821ab0dQQitemZ250586704653QQptZMotorcyclesQ5fPartsQ5fAccessories#ht_3796wt_791

 maybe find a tank and a seat and ride while you figure it all out slowly.

[Honda?]

Yeah I did some quick rough math and the very most I would be able to fit under there after relocating even the air box would be 3.5 gallons. And then I would have to subtract the oil capacity. I'm really iffy about a rubber bladder. I would rather have an aluminum or epoxy resin tank. Haha and after thinking about it using the tank would be insane. One tweak and seams will split.

As for the ebay tracy body crushed velvet isn't really my style. :p Don't worry about my riding time. I just put the battery and fairings back on my primary workhorse bike.

2004 R1100S

[bucky katt]

nice oilhead beemer! i wrenched for a bmw triumph dealer a few years back and i really got to love those bmw twins. i need an 1150r rockster badly.

[Franken750]

Hi Honda?

Yes! Me! )

I wuz thunking about that very thing last week.

But how did you calculate 3.5 gallons capacity?

I calculated 10.5 litres. (2.7 US gals.)

Investigating how I could form the sides of the tank outwards where the side covers are.

My oil tank is going up under the tank shell. Different shape of course. |:-|

No starter motor (real men ride cafe racers therefore much smaller hi-perf battery somewhere ...

Tank won't be used as a stressed member. (Nothing to be gained IMHO + lot of risk).

I'm aiming for 14-15 litres otherwise I may need to reconsider.


Look forward to hearing of your progress.


Cheers

Franken.

[Honda?]

The extra bit of capacity was if you could move the air box under the old gas tank area and use that space above the transmission to extend the tank.

With the air intake where the original tank was you could make cool air intakes!  Problem would be routing a logical intake to the carb inlets.

Btw I decided against the under tank plan. My tracy body is getting worked over like mad. Tank is going to wider longer and deeper for more capacity and lined with epoxy resin which works with todays gasoline.