Modern Vespa

the OG SI 24 on my Rally is reaching end of life due to warped body around the slide and the pressed in air vent idle jet without the hole in top. cleaning and a file keep it in service but I'm starting to not trust it. The float cover was replaced a few years ago when the needle would insist on sticking open or closed.

So this has caused me to finally dig out the 24G that I bought in anticipation of this event.

was looking for idle jets and air correctors and fining very few sizes, finally finding a thread where the idle jet can just be shortened.

Then looking further and finding that the same applies to the air corrector. Cool, just spin up the lathe...

But why bother? why not just run the longer E style jets and modify the air filter so they pass inside?

Then I started looking at my bell mouth and did a test where they stick up through the bell. bonus is the bell does not have to come off to change the jets. I know some of the bells already have these holes, but I don't see any of them being used with the G.

What else am I missing and not understanding about the 24G?

Linking P200 jetting notes from greasy

The 24/G is for a T5 is it not?

I like it, easier to get jets out for tuning.

it is, but that does not prevent it from being used on others.
The thing that first had me looking at the 24G was the lower height. That made room for a proper bell without compromise while still leaving enough room above it for air flow.

So the point here is to figure out what combo of stuff needs to be swapped out to make the switch. Orders have been placed, results to follow...

Spent some time on a Bridgeport with DRO today to properly pick up the center locations for all the jets and screws on the 24G.

My prior method of using a flat bed scanner was very close on the surface around the filter, but not so close elsewhere.

i would use a standard e carb
the g is not worth the hazzle
and no jets available = useless carb

the max 0.5-1hp its maybe better
is killed by fearfull carb setting
wrong exhaust/timings etc

better focus on factors with bigger easier effects
intake and cyl timings. exhaust port shape and width
exhaust choice

and u easily exceed the limit where si technically
doesnt make sense anymore and u need a bigger carb

shun the nonbeliever, shun...

the shortage of jets is not real, I can use any E jet I wish in the G.

work in progress

integrated bell intake and float bowl cover that uses a threaded in float needle seat.

I will happily be a test subject for said endeavor. but also...

Put a new bell design up on shapeways for the 24G with holes to allow the use of the taller jets

Nice work Patric.
Totally makes sense to use the bell mouth design you whipped up allowing std jets to be used. Like!

Screw in seat also an interesting idea for making it properly serviceable.
Would that also allow for adjustment of float bowl fuel height?

I've used the 24G in place of a 24E and also a 20.... it's a modification that was done a lot and still is on this side of the pond. We cut the "jetting stack" down to fit the dimensions and worked a treat.

I've also had to modify the air corrector from the 24E to fit the body of a 24G when jetting a polini barrel with a Suzuki piston modification on a T5 before now. The parts are interchangeable with some modifications... and no penalty to be had that I can pass on.

Go for it I say!!

The fiber washer is 1mm thick standard so swapping to a thinner or thicker one would adjust the fuel height. Also the needle seats come in different flow sizes from 150-225.

https://www.dellorto.co.uk/shop/dellorto-car-carburettors-parts/parts/drla-parts/needle-valve-and-seat-150-225/