Building a big engine HELP

IM now in the process of having a big px engine built to go into a 1959 vba 150 basically im wanting to keep the look of the 8 inch wheels so what can i do about the gearing??

and what kits/exhausts/and general tuning kit should i be buying for this px125 engine[:smokin:]

T5Berks [:)] do you know what was done to the barrel on that reedspeed 166?? that set up as standard should be about 15-16hp i’ve been told that you could only really expect to get maybe 20hp tops due to the limited transfer area on a vespa?

I’d be keen to have a little look at that motor [:)]



well im wanting to build it so its very very fast is the 177 the biggest ???

i was thinking about a 30mm carb with reed valve etc etc etc but i aint bought this sort of stuff for years so dont really know what everyone else does nowadays

any help



ok, so you want to go fast with PX 125 base.
The most powerfull kit sure is the malossi 166.
Polini 177 is the second most powerful one.-
Pinasco is a good touring kit.
DR is a base tuning for the one that want just something more without too much change.

The difference between the two most powerfull kit is this:

Malossi 166 power curve is more high rpm oriented and this has to be taken in consideration for gearing ratio.
Malossi benefits from reed intake.

Polini 177 power is more mid range oriented.
More beef in this range. Good torque. Easier to set up. You can drive longer gear.

I have built engines with both kit and for my personal taste I prefer the polini kit. For me the Polini power range makes more sense for a vespa that has just 4 gears.
The thing is all about feeling, how do you like your engine to be.

I can give you some specification of a Polini 177 engine I did that I
like to drive:

-Polini kit
-Cranckshaft longstroke worb5 special lip.
-cluster from PX200 primary 65
-cosa clutch drive 21 or 23 teeth (depends on the exhaust)
-Exhaust RZ right hand
-head gasket 1,5mm (you had to use this with a longstroke. I have tried 1,5mm base gasket. With Polini better to use head gasket)
-Carb. of all the carb I tried the one I prefer is the Keihin PWK28
if you ever going to use one ask me for setting since the good setting for polini 177 is not close to the standard setting.

  • Malossi reed (Polini 177 doesn’t get that much better from it, but if you want the most you can get out from a kit this is the way.)
  • Crancases ported and inlet port modified to fit reed intake.
  • Polini barrel porting modified and piston modified.
  • PK modified for PX flywheel.

With a kit like this is of the most importance to set the carburation right if not you are going to size for sure. And you have to set well the ignition at 17. Spark Bosh W3AC or NGK9HS.

If is set up carefully is very rekiable, start at half kick, and vibration is very well controlled.
I drove with this kind of set up for 6000km and 0 problem.
Top speed around 135kmh with 23/65 gearing.

You can get even more power if you use a 30mm carb. But Icompared the 28keihin with the 30 dell’orto and is better keihin.
I used Mikuni tmx 30. A little more power than keihin but Mikuni body much bigger than the keihin and you need some modification to the manifold if you use the malossi reed block.



27hp from Malossi 166 ?!?
Already getting out figure of 23hp needs a lot, a lot of work and big carbs.
What can I say from experience is that
whenever you go over 21hp with smaller then PX200 kits you will loose reliability since you have to get this HP out from very high rpm and these figure are not easy to digest from a vespa engine
smaller then 200.


superb info there m8 pretty much what im going for 166 30mm carb and malossi upgear kit and a racing crank aswell[I)]


what kind of kit to use and exhaust depends on what you are looking for.
If you are looking after a mild tuning you could use either a DR 177 or Pinasco 177 kit with PK modified for Px flywheel.
Carb. 24/24 si.
As far as concern the exhaust the best on the cheaper side is the Simonini. If your economy allows you could go for something more exotic as SIP or RZ but these exhausts will come out on the left so must judge your taste.

  • In any case if you intend to use 8 inch tyre, you have to use a 23/65 of PX200. Or you will have too short gearing with PX125 engine.

You can keep the output shaft of PX125 so you will have a shorter 4th and then change all the cluster (christmas three) with a PX200 one so it will come with the primary of 65.
It is much easier to change all the cluster then only the primary.


cheers ozzy [I)]

don’t get a DR kit [:)] they’re a touring kit and don’t go fast, they’re more like a steam engine… I’ve been experimenting with the malossi 166, it’s a bit smaller but has really decent power output, it’s just really well designed. also it’s bomb proof. there was an artical in scootering with some bloke who had reedspeed ( i think??) tune one to a claimed 23hp!! thats mega hp, not sure how true though [:)] I’m running; 166, 30mm delorto, reed conversion, t5 flywheel, race crank (should be a full circle but can’t afford it) and a BEERACE exhaust. it goes like the clappers and sounds great. as far as exhaust’s go I’ve had a simonini on it and a leovinci as well, for cheap exhausts they’re both ok, the simonini is the better, it just has more practical power, even though the leo has better top end, but at the end of the day a decent expansion chamber is the only way to go fast, you won’t find a BEERACE pipe as I don’t think you can buy them yet, but its really good and when he starts flogging them proper, I’m sure sip forum will get to know about it.

i’m sure others may disagree but as far as I’m concerned the 166 is the better kit to go for, its good and revy with a good kick of power, and it won’t break. you could try and find a price for a fabrizi kit or a zirri kit, I haven’t heard a great deal about them, but I reckon they’d both go like stink.

ozzy [:drink:]

Just in reply to Ozzies earlier post about the reedspeed scoot. The scoot in question is owned by a good mate of mine and was at Reedspeed when he was having it set up again on the rolling road. Reason it was beeing set up again…It did have 27 bhp but it was crazy to ride anywhere apart from on long stretches of road, so he had to get it back to 23bhp. Still shit fast tho. Eats clutches like no ones business tho.[:shock1:]