Modern Vespa

Anyone used one of these?

http://www.sip-scootershop.com/en/products/float+chamber+cover+pinasco+_25293102

Buy the Cosa instead, and remember the needle. Same but cheaper.

I'm planning on using it on a T5 24G carb.

Am I right in saying I'd have to drill out the hole I the float chamber?

My px float chamber needle was leaking badly so I bought
the cosa float chamber with the 5.2mm needle and did some mods...
With some careful mods it will be even better than the expensive
DRT or Pinasco float chambers:


5mm hole fuel line into float chamber>
Bigger holes to the needle + 2 more>
Most important hole: float chamber to HD 2 - 2.5mm>
Good thing about the Cosa float chamber is that you can drill
even the needle seat bigger (the px and cosa are 2.1mm), I
drilled it to 2.35mm and 3.1mm down just 4mm before the
needle seat>

Is fuel flow really the limiting factor, more so than the main jet?

This really interesting,

Have you fitted the cosa one yet tarifachris? How is it working?

So even if I bought one from our German friends if still have yo get the drill out?

Yeah. Even on some pretty highly tuned engines I've never run the bowl dry. But then again, if you run it below tge float level it's supposed to maintain it will dramatically affect how rich or lean the mixture is regardless of jet size. Interesting. Wonder what the needle is from. Looks like all the other mods could be done with a drill press to an oem one.

So get the cosa one and do it myself?

Actually you need only this hole... 1.8mm for 166 and 2,0mm for 210!
I needed every flow, because I run a malossi 210 with expansion chamber and Si24... now it goes 46 mph GPS in 2nd gear (8250 RPM)...

So could I just drill my existing carb?

Yes you could mod every float chamber...
Personally i am 5-8 numbers down in HD size.

I think the bigger needle was standard in the european Vespa COSA models. This needle alone will not fit a PX float chamber. The Vespa T5 with the SI24G Carburettor had the bigger needle/needle seat in the float chamber.

Yes, because this is the most important hole. But be careful not to drill to deep, measure it beforehand. I think it was 12mm deep. You have to drill with a longer drill or a dremel to access this channel.

2nd important would be to widen the 2 holes in the needle seat...

I had hoped if I'd bought one from SIP it would have ben drilled already

Some interesting mods Tarifachris. But what do you mean by the comment above, down compared to what?

any further info about this troops?

I've re-read the above post. I'm convinced I'm suffering from fuel starvation. I am thinking of buying a cosa float bowl and hope to drill the right holes. I don't want to touch my original T5 float bowl. I will also get a 5.2 float needle.

How many holes do I need to drill and where. I'm not exactly sure from the diagrams above

I would check fuel flow first... Tank vent, fuel tap, fuel line, float/needle. Unless your motor is heavily modified (and for some reason the carb is not upgraded also) , the Si in stock form can handle most motors.

Absolutely. Are you sure about that? I have 5 Dellorto and 1 Spaco carbs for T5, and they all have the regular PX float chamber with springless 4.5 float needle. From what I've noticed, the only actual difference between an SI24/24G and an E (T5 vs PX200) is the difference in height (10 mm).

Franks right

Usefull tips. Both hose and carb need upgrading

https://www.germanscooterforum.de/topic/171266-das-si24-26-spritzufuhr-topic-was-ist-zu-beachten-benzinhahn-schlauch-nadelsitz/?page=6

https://www.germanscooterforum.de/topic/92368-24-si-vergaser-optimierungstopic/

There's something odd going on with the above video. It looks to me that the Cosa needle (which is slightly taller than the un-sprung P needle) is blocking the flow out the side holes.

Thanks guys, that makes it a bit clearer

Fuel pressure with a low tank is a limit factor, I'm sure everything done to improve flow is a gain.

I've mentioned on the Pinasco 225 thread that I am having fuel starvation problems, and noticed this thread in a search.

I'm about to order the Cosa carb top for my 24/24 (with float bowl to jet already drilled to 2.5mm), but wondered how others had faired sorting their fuel issues?

Are the SIP spacers still available? Do they work?
Are there specific fuel pipes that aid flow?

I've got a BGM fast flow, but actually read somewhere about the potential for trapped air causing problems with the BGM fast flow tap??