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

From now on is the new one Polini 221cc Vespa cylinder available from us.

What's new?

  • suitable for 60mm stroke (long stroke shaft)
  • reinforced outlet with steel ring
  • massive, centered cylinder head with large cooling surface
  • also fits E-start engines

Dimensions and data:

  • Cylinder height 99,7mm
  • Outlet height 39,2mm
  • Overcurrent height 50,2mm
  • Support channel height 53mm
  • Cylinder base gasket 0,25mm
  • Cylinder head gasket 0,25mm
  • Outlet chord 36,8mm
  • Compression ratio 10,2: 1 (with QK 2mm)

Polino 221 (3)

We took a closer look at the Polini 221ccm cylinder for you.

Polino 221 (5)

Solid cylinder head

At first glance, it impresses massive cylinder head. Equipped with additional cooling fins on the underside, it ensures sufficient heat dissipation at all times, even with engine concepts that are subject to high thermal loads. The spark plug thread is designed for long threads, i.e. a B9ES or Bosch W3CC for NGK.

Polini 221 centering pins cylinder head (4)

Precise centering thanks to centering pins

It also has centering holes together with the cylinder. With the included centering pins, the pinch edge can be set safely and precisely.

Polini 221 Centering Pins (7)

Reinforced outlet nozzle

You can find another nice detail on the outlet nozzle.

Polini 221 outlet nozzle (6)

Here the sensitive aluminum socket is reinforced by a resistant steel ring.
The steel ring effectively protects the sensitive aluminum nozzle from damage by exhaust systems that are fastened with a clamp. Exhaust systems suspended by springs no longer “gnaw” off the exhaust port.

Suitable for engines with an electric starter

A little trick in the truest sense of the word adorns the outside of the right overcurrent duct.

Polini 221 franking e-start pole wheel

With the 221, Polini offers one of the few cylinders available on the market that can be installed and driven with an electric starter without any changes.

Polini 221 franking e-start pole wheel (13)

Measurement results

Here are the usual ones Scooter Center - Measurement results:

Height cylinder: 99,7mm
Outlet height (from OK): 39,2mm
Overcurrent duct height (from OK): 50,2mm
Support channel height (from upper edge): 53mm
The piston residue is 2,0mm with the included cylinder base gasket

This results in the following control angles:

Outlet 168 °; Overcurrent 120 °; Support channel 104 °

Compression ratio and combustion chamber volume:

In order to determine the combustion chamber volume and thus the compression ratio, we rented out the cylinder head and determined the volume of the dome of the piston crown.

Polini 221 combustion chamber volume (11)

The combustion chamber volume of the head is 24,9ccm.

The volume of the elevation of the piston crown is 8,1 cm³

With a piston residue of 2mm and the resulting squishy edge (without the enclosed cylinder head gasket 0,25mm), the compression ratio is 10,2: 1

Based on the moderate control angle and the combustion chamber design, together with the Polini crankshaft, we would expect an engine with good running smoothness and a lot of torque in the lower to medium speed range.

We are excited to see when you will put the first real Polini 221ccm on our test bench!
Polini 221cc Vespa cylinder now cheap at Scooter Center Kaufen.