Polini 221cc cylinder

Update: Malossi MHR 221ccm cylinder for Vespa PX 200 available Malossi MHR 221ccm cylinder

As with the new one Malossi Sport and MHR cylinders , we also dedicate ourselves to the details of the Polini 221cc cylinder for 60mm stroke crankshafts. We had already measured timing & co for the Polini 221 cylinder for the Vespa here: Polini 221ccm 60mm long stroke.


The one included in the cylinder kit cylinder head is also with the current Polini 210cc used. Polini regulates the adjustment of the compaction simply by changing the pinch edge.

So let's grab the head and give it a suitable one Long thread spark plug and simply apply grease as a seal for our plexiglass instrument.

Cylinder head Polini221

With the Plexiglas plate in place, we fill the cylinder head with the burette in order to determine the exact cylinder head volume.

Cylinder head Polini221_2

The meniscus remains in our burette at 25ml. The volume of the combustion chamber in the cylinder head is therefore 25ccm.

To get the entire combustion chamber volume (Vc), we still need the volume of the domed piston crown. With a defined piston backing, in our case 6mm, we first calculate the volume of this “cylinder”.

piston head polini221
6,85 x 6,85 x 0,785 x 0,6 = 22,1ccm so is the volume.

Also sealed with grease and filled with lamp oil in a playful delicate rose, the burette reveals a value of 14,6ccm. So 22,1 - 14,6 = 7,5ccm for the Volume of the piston crown.

3_bottom polini221

The last ingredient is missing Volume of the pinch edge. Measured directly on the living object, i.e. directly on the engine, this is 2,2mm, which in turn has a volume of 8,1ccm requirements.

Combustion chamber volume

So we come to a total combustion chamber volume of:

Cylinder head 25ccm + pinch edge 8,1ccm - piston bottom 7,5ccm
= 25,6ccm

compression ratio

Does this result in a compression ratio? from
Cylinder displacement 221ccm + combustion chamber volume 25,6ccm / combustion chamber volume 25,6ccm
= 246,6ccm / 25,6ccm
? = 9,63

Polini 221ccm cylinder put to the test

Here is another example of the Polini 221 based on a customer engine.

So Polini 221cc, Polini crankshaft 60mm stroke, Dellorto PHBH 28, Polini intake manifold for rotary valve and ours bgm BigBox. With the original cylinder base seal, control angles of 120 ° / 170 ° result. For more information, see the diagram below.


For a motor that is only plugged together, i.e. has not undergone any machining of the channel surfaces, 26Nm is a reasonable amount of torque. Especially when power and torque are available that early.

At 4000 rpm, 20Nm are already available, which is at least twice the value that an original PX200 reaches as a maximum.

Depending on the gearbox setting and application preferences, one can confidently longer primary can be used to achieve a solid cruising speed at low speeds on the motorway. The low-vibration running of the Polini crankshaft then contributes to the rest of the comfortable journey ...

120km / h cruising speed

With this motor and a longer reduction ratio should permanent 120km / h to be possible. Here ** as an example, once with the original gearbox and once with our bgm Superstrong clutch and DRT pinion extended by one tooth on the original primary of the PX200 with 65 teeth.

PX200 24_65

Since there are still 7000PS at 20rpm, it is possible to crack the often cited 120Km / h mark.

** The gear calculator "GearCalc" was kindly made available to us by GSF member Motorhead. Thanks very much!

Cylinder -POLINI 221 cc aluminum, 60mm stroke- Vespa PX200, Rally200

Article no. P1400084

Cylinder Polini 221 Alu Vespa PX200

Polini's plan to bring the well-known 210cc aluminum cylinder for the PX onto the market in a long-stroke version (we reported), is finally taking on concrete forms.

Cylinder Polini 221 Alu Vespa PX200The new cylinder, which is presumably the well-known 210ccm cylinder (but with a longer raceway) in terms of layout, is delivered with a special cylinder head suitable for the stroke of 60mm. Further details such as control angle, compression and a performance specification are unfortunately not yet known, but we will send them as soon as available.

The The cylinder head is also available separately, since, according to Polini, it also fits the kits made of aluminum and gray cast iron with normal stroke. One will see how this is solved and what the interesting side of the head looks like.

We have published here what the 'normal' version of the Polini with series stroke (57mm) can do:

Polini 210 Alu Plug & Play

Polini 210 with processing

A special, self-made long-stroke version has already been tested here:

Polini 230cc

We expect one from the new version even broader performance curve than with the 210ccm variant, as the control angle inevitably increases through the use of a 60mm long-stroke shaft. Hopefully Polini will counteract the disadvantage of an excessively high overcurrent angle by adapting it by extending the cylinder's path. This would certainly result in an engine concept that many would like for everyday use: A lot of pressure from the low rev range, a strong middle and sufficient revving power for the motorway. The whole thing without the thermal balancing act of the old cast iron cylinders.

Polini also offers a crankshaft with a 60mm stroke to match your cylinder:

Crankshaft Polini PX200 60mm stroke for aluminum cylinder 221ccmPolini speaks of a very well balanced shaft which, thanks to tungsten inserts, should run with very little vibration even at high speeds. A modified intake time should also release more power. Here, too, we will submit all further information as soon as we receive it or have checked it ourselves.

The cylinder can of course also be operated with any other PX200 crankshaft with a 60mm stroke. A high quality and The significantly more cost-effective alternative is here bgm PRO Long stroke shaft which already proven in countless very powerful engines hat:

Crankshaft PX200 Lagnhub 60mm BGM pro

With currently €179,99 it is significantly cheaper despite the highest quality material (connecting rod + bearing!) and offers a sensibly extended inlet control angle perfect power package without the disadvantage of many other waves of spitting back into the gasr.

And finally ... Here, too, Polini is making clear its pioneering role in terms of product innovations for switch scooters. While competitor Malossi is currently limited to giving a new coat of paint to tried-and-tested but aging products simply by assigning new item numbers, Polini shows what you can do with tried-and-tested parts but a little more courage and innovative spirit.

In terms of price, the cylinder will certainly be slightly above the 210cc cylinder move because the long stroke kit is delivered with a cylinder head.

Cylinder and shaft together offer a high-capacity touring package that with a little attention to detail will certainly scratch the 20PS brand without having gear connection problems.
What more do you need?

Certainly one of the nicest innovations for PX200 drivers since the invention of the BGM Superstrong Cosa clutch...