Modern Vespa

Hi all,

Long time away from the board. I am thinking of having a local machine shop bore out a spare si24/24e carb that I have to 26mm (and to drill the fuel supply hole to the main jet to 2mm).

I am not sure what it is called -- the brass tube in the carb throat -- spray bar, something like that? Anyway, how can that be removed? I grabbed it with some small needle nose pliers and pulled but it didn't budge and I was worried about squashing the tube.

Thoughts?

Never thought about it, but…
as long as it wasn't put in before casting with some sort of positive geometry inside the carb - then I would expect heat would allow you to remove.

If me:
Torch on carb wall all around tube to get that area nicely hot.
Then see if you can wiggle out with pliers.

Other ideas:

Put a small steel rod (welding rod?) inside the tube first, to keep it from squishing and soak up some heat.

Use iced steel pliers so they cool off the tube when you grab it. Dunk em in ice water for 5 min.

Let us know how u make out.

Nozzle is pressed in through the plugged hole marked in the photo. I don't know if it's worth the trouble than buying a new one…

I wonder if it will work better after doing that.

the new ones that are bored to 26 have some ridiculously thin sections to the point that the one I bought just sit's in a box, will not be installed.

I think the Vortex had tapers machined above and below the spray bar, and this seems like a much better idea.

OK thanks for the tips. I'll not pursue this route. I'm trying to cure apparent two-stroking at 1/8 throttle on a Malossi 210 setup with an SI24 carb. I've got the standard setup, the bike runs great when the throttle is more opened, but I can't get the low-throttle part smooth. I'm running the standard 160-BE3-125-ish main jet stack and started with a 55/160 idle jet and played around with changing those, but can't get it perfect.

Now I see myself desperately looking at SIP's $40 slides, maybe that's the problem. Down the rabbit hole...

the vortex had a bit of taper and some cut into and shortening of the spray bar. I don't have one any more to snap some pix, but that seems to be my recollection.

T5 slides are richer. They have no cut out for air and it's cheaper.

https://www.sip-scootershop.com/en/product/throttle-slide-dell-orto-05_84920500

Or plug off the oval hole above the slide.

Your issue could be lean, could be rich.
That spot is a particularly tough place to knock out with performance engines and larger carbs.

You might find the 26 worse.
the suggestion above - to try a different slide - is not a bad one.
You could mock it up with some epoxy filling the dish in your current slide.
Or buy new.

Smaller throat carb would likely be easier to tune in that area - but may rob your top end.

If you're looking at the Lemarxon slide, keep in mind it's part of a mixer + slide system.
X234 atomizer & LM-L slide should get you as close as you can to 1/8 smooth. If you want to chase that rabbit further down the hole, add the XX34 and LM-M.

You can find similar setups on this page. Click on the pics for each setup.
https://www.facebook.com/media/set/vanity=623198641104514&set=a.5323766011047730

Isn't a two-stroke supposed to two-stroke.

Can you avoid 1/8th by increasing the idle a bit?

Last edited by waspmike on Wed, 20 Sep 2023 14:25:16 +0000; edited 1 time

the one eighth four stroking gurgle plagues us all. Ive given up trying, we've had so many posts on this on MV. Quite frankly, id rather know my scoot wasnt going to explode as most of the time I ride 3/4 to full throttle every day to work and back, scoot never misses a beat and spot on avoiding seize territory. Just dont run at 1/8 throttle, change your gear up, it improves slightly. I was also under the impression as to the rich lean question that slightly pulling your choke out answers that question, in my case it makes it worse hence I believe im rich on 1/8 and quite frankly i use my nose too, cause you can smell its rich pottering on 1/8th, run around the block a few times four stroking, cut your ignition and see your plug is quite wet/black, sight, sound and smell buddy and you know whats what IMO.

Lemarxon slide and mixer tube ordered! Thanks for the tip. I'll post the results after it arrives and gets installed.