Modern Vespa

P125x
SIP road 2.0
24.24

After giving up with my DR 177, have recently fitted a VMC Super G 177. What jet stack/ carb combination have people settled on? Same as DR or different?

VMC Stelvio (alloy cylinder vs your Super G):
140ac with a drilled/Cosa filter. Rode similar with a 160ac and original filter.
BE3
128mj city. 130 touring.
55/160 pilot jet.

All modified bikes are different, as well as your weight, gearing, climate, etc...

This "should" sort you out. At the least, you'll have a jet set from the same manufacturer, and not chase your tail as much as otherwise:
https://www.scooter-center.com/en/carburettor-tuning-kit-nozzle-set-bgm-pro-for-vespa-px125/150-with-bgm-pro-177-cylinder-kit-main-jet-set-secondary-jet-mixing-tube-air-correction-jet-bgm1770nej

Thanks for that ^^^, some good info here. Seems like a good set to have for most any similar kit. And what do we think of this logical comment? I know that serious Cosa ppl usually say that to run properly don't mess w/ the carb, weird Cosa air bellows or the filter plumbing to the second big filter under the seat.

Thanks for this. I will have a look through the info.
i should note a couple of things. The air filter is a px200 with pre drilled holes. And today when I went for toodle it was 40 deg C (Dubai). The CTG quickly got up to 350 deg f with quarter throttle and doing 60-70k. This was a lot quicker temp rise and at lower speed than the DR. I would lean off the throttle a little and the temp would come down. The high temp at low speed makes it dangerous to ride here in Dubai. How do I reduce the temp for 1/4 to 1/2 throttle. Still running in also.

This may help,

Guide: SI Jetting Chart + How to Tune an SI Carb

My super g with a polini box and a drilled filter is running well on ac160 be3 mj128 and a 55/160 idle. Remember all bikes are different but it will give you a ball park of what you are aiming at. Remember the mantra jet rich and work your way down. I started with a 135 main.

My is
AC 120
BE 3
125
55/100
Mix 2.5 out

Polini Box, ports not matched, original drilled air filter and drilled SI 24/24

Maybe this thread give some help.

Thanks for all the direction. Just been out for a 100km run. It's 35deg c.

From the guys who gave me their stack numbers I have put in:
AC 160
BE3
MJ 128
55-160

For context:
P125x
Unported
Px 200 filter with holes
24.24 carb
SIP Road 2.0
Temp 35 deg c

Still running in so only between 1/4 and 1/2 throttle

Starts first kick (new one on me)
1st, a little spluttery but not 2 bad through to half throttle. Could be smoother.
2nd fine
3rd fine, occasional quick stumble. Kept slowly accelerating when throttle kept between 1/4 and 1/2.
4th, fine. Kept slowly accelerating when kept at between 1/4 and 1/2 throttle comfortably upto just over 80km/hr

However, still getting hot. Not as bad as last week. But in long runs had to keep at 60-65ish to keep at 330deg f.

I will follow the guidance on finding optimal jets etc once I have run in and can take to WOT. But anything anyone can point wrt the temperature?

330F is not a little bit hot for crusing round on half throttle. The AC160 is way too lean, especially with a drilled filter. AC120 will run much cooler. More power at high rpm too. Will likely need a bigger pilot jet before it's finished.

With a drilled filter you're effectively increasing the ac's size.
160 no holes, 140 drilled/Cosa filter, 120 no filter worked similarly here, and safe.
You're close to a 185 ac/stock filter with that 160.

The ac both leans/richens and determines when the main circuit initiates.
Smaller = earlier.
A 120/Cosa filter initiated the circuit too early at this level of tune.
I couldn't get it to work as both a city traffic rider and cruiser.

The slide cutout is most in play at mid throttle. You can test its leaning/delaying influence from around 1/4 to 3/4 throttle by taping over the oval hole at the top of the carb that feeds it.

Go baby steps! One change at a time or you'll go nuts.
First step 140 ac, or filter without holes.

Adjust the mixture screw on the road. From a rolling stop in second it should pull smoothly up to 1/4 throttle (where that circuit is dominant). This can be anywhere from 1.5 to 4.5 turns out.

Btw I'm assuming you have enough fuel flow and no air leak(s).
Fast flow tap. Channel from the bowl to the mj drilled to min 2mm.
8mm (5/16") x 24" fuel hose. Hopefully a carb reworked in Europe vs a Spaco out of the box.

Hi Ray and Jack,

Thanks for this.

I have a 140AC so can try that, i will buy a 120AC also, but dont have an undrilled filter (would you recommend to replace?).

I have read about the drilling of the float bowl but dont undersatnd why. Any threads here for my understanding?

I have a fast flow tap, new ish fuel hose and the Dellorto 24.24 is also new ish.

Jack, you mention larger pilot jet, what should I get my hands on?

Undrilled filter is ok. Start with the AC140 you have. Reduce the Main jet size from splutter, until WOT feels heavy, then reduce one more size until it feels good and revs freely. Once you have this jet size, the rest can be determined. Only worry about WOT for now, all the other coughing and spluttering is easier to fix when WOT is done.

The pilot jet needs to be much bigger than stock. Typically on a bolt on kit a 50/100 will adjust in close enough. If you have a BGM set of the 58/160 to 68/160 sizes these can be enough to work.

Sorry for digging out the old thread. Didn't wanted to create new one with the same topic.
Here's mine.
PX125E with replaced: Cylinder/piston,etc VMC177 Super G, carters fully ported, carb SPACO 24/24 with drilled passage, filter without holes, exhaust SIP Road 2, new crank Mazzuchelli.
So after many strange suprises and reworking of carters the engine was installed into scoot. Since 6 months (didn't had too much time) I'm struggling with carb adjustments and jetting. I went thru all forums, almost made PHD from SI jetting and I think I'm still somewhere in front of wall of dumbness.
I've tried many combinations and my current setup, the best I could find is still not as I've expected. Starts from first kick, rides to 1/4 nice, 1/4 - 3/4 lot of spluttering, WOT after a while OK, reducing to 1/2 - 3/4 still works fine.
However getting too hot. After a 10 - 15 miles ride it takes 300 - 320F. Still cannot find where are the 16HP?
My current setup - the one which rides acceptable smooth is:
AC160/BE3/122
IJ 60/160.
2 turns out.
Any bigger MJ makes scoot unrideable.

I struggled dialling in also. The guys on this thread were great so perhaps go through the thread. I ended up with:
BE 3
128
AC 140
55-160
After about 4 goes. It still sputters 1/4 to 1/2 in gears 2 and 3. But pretty good.
My cases are not ported and this could have a big impact.
I am sure the real experts will chime in as they are great!

When I first did a Super G on my Stella, I could not get it jetted properly with an air filter. I quickly ditched it and ran no carb mounted filter, and used either the bellows to the frame or a UNI foam pod filter mounted to the front of the airbox. This made jetting much easier and more predictable and I never looked back.

My setup at the time was:
VMC Super G 177, no case porting
SI 20/20 with float passage drilled
GGR Hot reed in stock reed block
SIP Road 2 Sport exhaust

52/140 1.75 turns out
140AC/BE5/130main


I have only messed with my Spaco 20/20 so I don't know if this applies to Dellortos, but down the line I had strange lean-out issues that I could not figure out. I eventually found that it was the OEM spring-loaded float needle closing the fuel off early and restricting fuel flow, causing the bowl to empty under extended WOT. I drilled out the fuel inlet banjo for more flow and replaced the float needle with one from scootermercato's rebuild kit (one solid piece with an orange tip). This solved the starving issue and the banjo drilling increased fuel flow by about 40%!

Thank you guys for information about your experiences with carb tuning. Unfortunately we have different setups so your solutions cannot be directly paste - copied into mine.
Looking at my spark plug I see that I'm running way too rich. Probaly on idle side (main side is leaner that suggested everywhere - 160/BE3/122). Unfortunately leaning idle even with adjusting the mixture screw do not have satisfactory effect on scoot behaviour during ride. On leaner idle jets there's no power, higher revs are very hard to be reached and richer main jet setup (i.e. 160/BE4/125) do not help to cover the idle leanless.
In summary when I'm too rich on idle side and to lean on main side the engine power response is the best for now (but still below expectations). And this is my main headache. Where did I made a mistake?

On these carbs, if the main stack is too lean, the pilot stack, once away from idle (progression), will also be too lean, even if the pilot jet is huge it will not compensate.

Everybody else has an AC140 fitted on the main stack. I suggest you try the same.

I've kept with 160 because undrilled filter. Just right now I installed new spark plug BR9ES (before was B8ES) and changed idle to 160/58, 2,5 turns out and also atomizer to 140. The result? In the low to middle range of revs starts good then a lot of sputtering and I could feel when main is becoming dominant. When this happens the power and revs increase very easily and then I can feel the power of this setup. It was 20 km ride, temp reached 154 C (320F). So I think the idle to be sorted. Spark looks as on the photo