Modern Vespa

Have been working on a custom seat/tank for my Rally 200.

After a bit of playing around have come up with a mockup in card that should be a great starting point and when upholstered shouldn't look too different from the original Super Corsa seat.

I chose this as the starting point as love the shape of the seat (especially as I'm taller) and the "hump" at the rear gives a good spot for the fillcap.

With upholstery will be a little taller than the original - aiming for an extra 10 litres of capacity.

Have added a 1.5cm high step and angled the rim of the seat at the front for air intake through the frame - and another at the rear so a standard rear rack can be used.

This is 14cm wide - hopefully this is enough - haha

Other than this have tried keeping the construction as simple as possible with flat sheet rather than curves - am expecting once upholstered these edges will be softened.

I've created a 2cm lip around the bottom edge to attach the upholstery and so the seat blends in with the profile of the scooter etc - might add barbs/hooks underneath to attach the upholstery.

To attach to the scooter will have lasercut brackets that bolt to the standard mounting points front and rear, these will be accessible from the front and rear stepped sections.

The mount points on the seat/tank will be designed to be modified etc if needed rather than into the main tank body.

Would love any thoughts or feedback - or if there is anything obvious I've overlooked.

Very cool idea! Looks well thought out. It looks huge for added capacity. The angled edges on the top/sides are a nice touch.

Cheers!

I'm sure I've missed something crucial but will be an interesting thing to test.

Should end up with 18 litres of usable capacity which I think should be more than enough

Very cool..
Are you making more than 1?
Or that should have read CAN you make more than 1?
I would love more fuel!
No need for the seat though, just tank.

The only thing i think i'd do different is to relocate the filler cap somewhere else and not make it recessed. Aesthetically it looks good where it's at, but i'm guess you'll loose out on holding 1~2 more liters.

Plus weeping into the foam.

Also if the cap has a breather there will be a trail of fuel following you down the road when fuel sloshes against cap
How do I know?
Well, I know!

BTW: is foam fuel-resistant? Some polymers will dissolve in petroleum distillates... lemme know if you need good info on chemical compatibility

Thanks for all the insights, very interesting points!

Thinking a seperate vent with a hose might make the best sense, where would the nest place to run this under the scooter be?

Obviously not anywhere it can end up on the rear wheel etc?

I'm running a reed block and a 28mm Mikuni round slide so could it be plumbed into this somewhere?

Vent is normally ABOVE fuel level, otherwise it's just a stphon hose waiting to start

Very true, will do some research into the best location in the tank and to vent too.

Modern scooters seem to vent to the bottom of the engine casing away from the wheel.