Hi all,

some months back I bought a ex SA PMG VBC 150 in bits that required reassembly & repair.

It is now back together and going on club plates next week.

Even though it is no rocket ship I have read that the performance may be improved a little by replacing the S1 20/15 carby with a S1 20/20 unit.

Have any other club members had experience with this upgrade & could recommend set up re jetting etc? Engine internals and exhaust are standard.



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Hi James,

I did what you are proposing to my VBC 150 Super… and more! 

Many people looking for an old Vespa tend to pass over the humble VBC with its little 8” wheels but long time owners come to appreciate its ability to whip around a tight corner. Mine’s done close to 150,000 kms now and I would never get rid of my beloved Priscilla. 

Many years ago I replaced my standard carburettor with a Dell'Orto SI 24/24 for a PX without an oil pump. Does your model have auto-lube? I chose one that had been modified by DRT (Denis Racing Team) with a bigger float valve needle and a larger tube drilled into the carb body to the main jet. You will also need a PX air filter to match the larger carburettor throat. 

Dell’Orto SI 24/24 Carburettor modified by DRT

PX Air Filter for above Carburettor

While SI 24/24 will give you a bigger fuel charge, you really need to match this with an appropriate exhaust. The SIP Road 2.0 exhaust is fabulous. Strong, torquey, not too loud and very well made. A bracket has to be modified slightly to fit on the Super. You will also have to increase your main jet from the standard 98 to around 105. This combination will give your Super a nice little lift which I enjoyed for quite a while.

SIP Road 2.0 Exhaust

106 Main Jet

But wait… there’s more…

You can turn your Super into a pocket rocket with the addition of a 177cc cylinder kit. If anything is worn in your current engine such as rings, piston or cylinder, then such a kit replaces all those things effectively giving you a new motor that is cheaper than a rebore.

My Super will pull up almost any hill in top gear and we laugh in the face of strong head winds. 177cc kitted scooters will usually outperform a standard PX200. The reason I suggested the SI 24/24 carburettor rather than the smaller SI 20/20 is that it gives you a future upgrade path to a 177cc kit which will need a bigger carb. Those fuel flow modifications by DRT also ensure that the larger capacity cylinder has enough fuel at full throttle. 

I put a Pinasco kit on mine which comes in either cast iron or alloy versions. The Pinasco is more conservative in terms of power than the Malossi or Pollini kits but it is very strong and well made. Mine has done around 56,000 kms so far. The Pinasco is plug-and-play so there is no need to match the engine case ports to the cylinder if you don’t want to. The big brother of our Supers is the Sprint. Although also a 150cc motor, it has a slightly bigger carb, higher compression and taller gearing for a modest increase in top speed. Later models of the Sprint (Veloce) had 3 transfer port engine cases while our Supers only have two. I believe some very late model Supers also came with 3 transfer port engine cases but the 150cc cylinder blocked one of them off. Pinasco have kits for a two port motor which have an extra window in the piston skirt that allows the fuel charge to pass through effectively making it a 3 port kit, although Pinasco claim 5-ports as this port splits into two within the cylinder wall. With a 177cc kit you’ll have to increase your main jet to around 122-125. I still have my original cylinder sitting in a box but I can’t see myself ever swapping back to standard as the 177cc kit is too much fun. I also get much better fuel economy from the larger cylinder. Go figure.

177cc Pinasco Cylinder Kit

But wait… there’s more…

Although you’ll enjoy the new found power of a 177cc kit, you will soon realise that you have enough grunt to push you along faster. The Super has rather low-geared transmission. Its easy to get up to speed with the larger engine but the RMP seems all too busy. There are a number of ways to up-gear. I am about to do it myself. Here is one of them:

Malossi Up-gear Kit

If you need any further advice just let me know. The old engines are easy to work on.

Best wishes, David

Hi David,

Thanks for all the information - there is much room for improvement!

I will have to save some pennies up for a while to go for the 24/24 carb and the SIP exhaust...

Until then...I have a 20/20 carburetor that came in a box of bits I got with the stock exhaust I bought....any idea of the jetting to start off with?  If I use the 20/20 could i manage to crack 80kph on a flat road? :)

P.S. the wheels are 10" on the 8" hubs. I assume the gear ratios are standard. 



Hi James,

As it came for the factory, the VBC Super was designed to have 8” wheels. If you have 10” wheels then something is amiss. Perhaps you have wheel rim extenders. That is, a metal annulus that allows you to bolt on 10” rims onto your 8” brake drums. If so not only won’t the brakes work as well as they should, but you will have trouble getting up to a decent speed if the transmission hasn’t been altered accordingly. Piaggio engineers got it pretty right across all their various models in terms of a balance of power, speed, fuel economy and exhaust noise. The choice of gear ratios was part of their considerations. 

As a guide to typical performance, a stock Super with a good motor should easily reach 90 kms/hr on the flat and a little more. I’ve had my Super since new and on my way back from Sydney in 1969 I was able to pass many vehicles on the Hume. Of course in those days there were cars and trucks from the 1940-50s but it was a quick machine compared to many others in its day. 

At higher speeds, a lot of engine power goes towards overcoming wind resistance. If your Super has a standard VBC gearbox then it may not have the power push along 10” wheels. The revs might be too low for the motor to get into a power band to cope with the very high gearing those 10” wheels give you. With 8” wheels, although the motor will be revving higher, it will be producing more power which will lead to a higher road speed. Do you know if the previous owner changed the gear ratios to match the 10” wheels?

The standard main jet on a VBC for the SI 20/15 carburettor is 88. I suggest you try a 100 or 105 main jet for the SI 20/20. You can find these numbers on the bottom of the 3-segment main jet stack. You can unscrew this once you remove the air filter. Don’t over tighten it when screwing it back. Here is a link that shows you how to dismantle a Vespa carburettor.


Let us know how things go and if you get an improvement.

Best wishes, David

Hi David, 

I bought the VBC from a man in Port Melbourne who was given to him by his father, so I do not know about the gear ratio change.

It had a problem with the cruciform gear selector mechanism....he pulled it apart and then found himself out of his depth mechanically....then asked a bike mechanic how much $ to put back together, I guess he did not like the answer and sold it on. I got it with a completely disassembled power unit and spent many a fun hour putting it back together, no probs have been working on cars and bikes since I was 13.

I did take a photo of the parts, maybe there is a clue in number of teeth??



Hi James, its great to see the photos of your Super in bits ’n pieces and nice to know this kind of work is not new to you. I've currently got my P200E motor apart all over the dinning room table. A leaky clutch side oil seal needs replacing. I assume you replaced your crankshaft seals when re-assembling it.

Members of our club have various specialist tools to make the task easier if you ever need to borrow them in the future. Like a crankcase splitter tool, and others to push and pull the crankshaft out/in of the cases without bashing on the shaft ends. As you probably will have discovered, the gears have to go back exactly the same way. They can't be swapped around as the cruciform won't line up properly. 

I’d go blind trying to count the teeth in your photo but I think we can assume its a standard Super gearbox. Here are the actual tooth numbers for a VBC 150:

Primary drive gears: 22 (clutch) 67 (layshaft)

Wheel shaft gears are:

1 13 teeth

2 17 teeth

3 22 teeth

4 27 teeth

So, have you got your girl up and running already? If so and you find it hard to reach 80 kms/hr then it will be those 8" to 10" wheel conversion rims shown in your first photo (love the colour of your scooter). The carburettor change may help a little but I think you’ll have much more fun going back to 8” wheels. Roberto The Vespa Wizard may have some 2nd hand ones. Otherwise 8” rims are available here:

GPS Imports SIP 8” Rim

Best wishes, David

Yes - up and running.

Off to the Mirboo North Italian Fiesta on Sunday.

70-75kmh with a tail wind

65-70 kmh with a head wind

...add 5kmh when a big truck goes past and you get in the slipstream...

While in pieces crankshaft bearings / seals replaced etc.

The Vespa electrical system done my head in to start with - yes! there is something more frustrating than Lucas electrics. I changed it all to 6 volt LED lighting and added a battery and rectifier/regulator.  

Going back to 8 inch wheels is something I will have to do - I would ideally like to swap (or buy/sell) my 4 10/8 inch wheels and tyres that I have for 3 8 inch tyres if possible.

Hopefully you don't have any guests for dinner while your 200 engine is in bits! 



Hi David,

I used a 55/160 idle jet and a 160/BE3/100 for the main "stack".

105 was a little bit too rich at full throttle. I think I have gained some extra performance (on Sunday I managed to reach 80 kmh a few times!) but the 10 inch wheels are holding it back - 8 inch wheels and tyres are on the way.




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