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Details Polini 221ccm cylinder for 60mm stroke

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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.

compression

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.

Polini221

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 http://www.scooter-center.com/product/P1400084

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Polini 221 long stroke

Polini 221 long stroke

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Polini 210 goes Polini 221 long stroke! - Scooter Center - Version -
We wanted him from Polini and reported about it in 2011. Now the Polini 221 long stroke is finally here! From Monday, July 29, 2013 at Scooter Center ScootersHope deliverable

Polini 221 long stroke

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

The “old” Polini 207 gray cast iron cylinder is a feared opponent thanks to its enormous torque, but due to the material used, it is not considered to be thermally very durable.

Thanks to the new Polini 210 Alu, this shortcoming is now a thing of the past. Due to the significantly better thermal properties of the hard-coated aluminum cylinder, the kit now runs thermally much more stable than its older cast iron counterpart. If the version for the standard hub of 57mm has already become a real bestseller, Polini is finally laying it at our request a version for the use of a long stroke shaft with 60mm stroke according to! This results in a whopping 221ccm, more than enough to get around quickly with a vehicle that usually weighs less than 100kg.

Overcurrent channels
The channel design of the cylinder was also adopted here from the well-known cast iron cylinder, but the control angles have been slightly changed / extended.

Performance
If the cylinder with 210ccm is already good for almost 15 HP and 20 Nm of torque on the rear wheel, the long-stroke variant adds several coals. The lower area, which is already very strong, is reinforced again, and the power peak and the band are expanded upwards.
Of course, the cylinder reacts with even more power to further expansion stages.

-Setup
Depending on the purpose, ours is recommended here

And finally ...

The Polini is the tractor among the conversion cylinders. Its full torque and the good pulling power predestine this cylinder for the long tour as well as for the next traffic light duel! Now even stronger with an extra 10ccm!

Short facts:

  • Bore: 68,5mm
  • Stroke: 60mm
  • Connecting rod length: 110mm (series)
  • Displacement: 221ccm
  • Cylinder head: Included in delivery
  • Piston: cast iron, 2 piston rings
  • Special: crankshaft with 60mm stroke required

Attention:

Please always assemble piston rings carefully. Piston rings made of cast material are only elastic to a limited extent and break relatively quickly.
Some pistons have trapezoidally profiled piston rings (so-called keystone rings), these only fit in one installation position. If the ring does not move freely, please loosen it carefully and turn it back into place 'upside down'.

POLINI 221 long stroke cylinder aluminum, 60mm stroke- Vespa PX200, Rally200
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Polini 230cc aluminum Vespa PX 200

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As already announced, Polini brings the 210cc cylinder in a version for use with a crankshaft with 60mm stroke (standard 57mm). The already available cylinder for 57mm stroke can only be driven to a limited extent with a crankshaft with 60mm stroke because the piston has an upper so-called L-ring.
This type of ring includes or forms the upper piston closure, so it controls the channels and not the piston upper edge as usual. If you now use a crankshaft with a 60mm stroke, the 3mm extra stroke must of course go somewhere ...

Since the piston moves 1,5mm more up and 1,5mm more down, the cylinder must theoretically be lengthened by this 1,5mm. For practical reasons, for the sake of simplicity, a suitably strong base or head gasket is simply used.
The problem with the two-stroke engine is that it also has an enormous influence on the exhaust and overcurrent control angles, which are important for the performance characteristics. To make matters worse, in the stupidest case you do not change both to the same extent, but usually take advantage of the overcurrent angle. Both values ​​(outlet and overflow angle) should always be in a ratio for the best possible power output.

In the case of the Polini, it looks like you are forced to use a foot seal. If you were to use a head gasket, the L-ring placed very high on the edge of the piston would simply rebound out of the raceway.
If a foot seal is used, the control angle is generally raised and, as already mentioned, the values ​​are taken advantage of in favor of the overcurrent angle.

This can lead to the engine starting too late with its power output and also being stalled in the upper speed range by a pre-exhaust angle that is too small (the angle that the piston releases the exhaust in front of the overflow ducts). This means that it can turn down further, but the power curve drops very quickly after the power peak.

In order to preserve the characteristics of the Polini, it would be better to recommend the use of a head gasket to compensate for the multiple stroke. As mentioned above, this is not possible with the standard Polini piston, otherwise the piston ring would rebound.

Facts ...

If the Polini 210 comes with 57mm crankshaft used, it has a very touring-friendly 123 ° overflow angle and 171 ° outlet angle.

When using a crankshaft with a 60mm stroke and a 1,5mm thick base seal this changes to approx. 135 ° / 179 °.
In other words, the overcurrent angle increased by a full 12 ° CA, the outlet angle, however, only by 8 °.
Both the absolute increase in both values ​​and, in particular, that of the overcurrent angle lead to a later increase in power. The whole thing can be done very well by using a tame, broadband touring exhaust system like one SitePlus, SIP Road be compensated.
The exhaust then still ensures good performance in the lower engine speed range, the greatly extended control angles allow the cylinder to rev up further in the upper engine speed range.

230cc ???
One of our customers (Thomas aka schoeni230) has exhausted the whole thing even further and a Polini 210cc aluminum cylinder with a special one 62,5mm long stroke crankshaft combined by Scooter & Service.
In order to avoid the problem of piston ring rebound mentioned above, the Polini was created here Piston against a counterpart of Grand Sport exchanged. This piston has only one piston ring and this is conventionally shaped and sits much deeper than the original L-ring in the Polini piston.

This made it possible to let the piston run out of the cylinder by the measure,
as the piston ring just gave:

 

 

 

 

 

 

 

As a result, the cylinder did not have to be lined very strongly at the cylinder base (approx. 0,4 mm) so that the control angle did not get too much out of balance despite a multiple stroke of a full 5,5 mm.
So the cylinder ran at ~ 133 ° / 179 ° and a special cylinder head that accommodates the piston in the head.
Due to the multiple stroke, the piston clearly undercuts the overflow channels at bottom dead center:
In connection with a modified Sito Plus exhaust (similar to the PEP3 exhaust), the engine impresses with its enormous torque in the lower rev range, an insane range and, measured by the exhaust type used, a very good top performance.

The carburetor was a 35mm Keihin PWK on a scooter & service Diaphragm intake manifold (myth V-Force membrane) used. One came as an ignition Vespatronic for use.

The cylinder has hardly been redesigned, only the outlet has been changed minimally in width and height.

And finally ...
Despite the very long steering angle, it is an enormously mobile and broadband motor that is sure to be the best for a touring rider. Full torque from the lower speed range and still still 20PS at well over 9000rpm.

Certainly not something that can be recreated, furthermore it is often problematic to let the piston extend that far out of the cylinder. Not only because of the then mandatory head centering to ensure that the piston does not hit the head, but also because of the increased thermal load on the zone above the piston ring.

The new Polini 210 for 60mm stroke will make the whole thing feasible for 'normal' screwdrivers, especially with a much cheaper 60mm stroke shaft. With it, many will certainly be able to build their 'dream' touring engine which combines a full torque with a wide speed range and a very good peak performance!

For those who find it takes too long for the 60mm Polini with 221cc to hit the market, this article encourages you to try out unusual combinations. Ie a Polini 210 for 57mm stroke with a 1,5mm base seal and 60mm crankshaft can also be expanded into a very nice touring concept.

In the sense of a well-known one (Harry B. from E.): try it, it works!

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