How to derestrict a vespa



Keywords: how to derestrict a vespa
Description: Ever wondered how to derestrict a 50cc scooter and make it go faster? This Tutorial shows every restriction on a 50cc scooter and how to remove it!

Over the next days/weeks I will explain the basics of scooter tuning, starting with simple improvements like derestrict a 50cc scooter and later going deeper into engine tuning concepts like flowing or changing the engine timings. Along with that I will also explain which parts should be installed first when starting tuning a scooter and which ones need to be replaced when getting more serious. Welcome to Part 1: How to derestrict a 50cc scooter.

Fast vehicles are dangerous. Derestricting a scooter makes it faster and therefore more dangerous to ride. Always ride within your limits and be aware that you might need a different drivers license when a scooter exceeds a certain speed or engine capacity. Also your insurance might not cover you anymore.

Removing restrictions and riding a scooter without having a valid drivers license is illegal. There are heavy fines and you might loose your license when getting caught or involved in an accident!

There are different reasons why scooters are having restrictions applied. It can be divided into three groups:

  • Environmental restrictions
  • To allow for use with a certain drivers license class
  • To comply with speed limits and legal requirements

This can be covered quickly as I only know about the catalyst applied to exhausts. Whilst it does not directly restrict engine speed it is still recommended to remove the catalyst when tuning a scooter. A catalyst has to operate at a high temperature to perform in its intended way. Unfortunately high temperatures should try to be avoided when increasing performance (increasing temperatures equal a loss of energy into heat).

The easiest way to remove the catalyst of your scooter is to replace the stock exhaust with an aftermarket model. Alternatively you can attach the exhaust of the same scooter model without catalyst (Minarelli and Piaggio engines have usually equivalent models with a non-cat exhaust). Beware as the stock exhausts are usually much more expensive than an aftermarket part and at the end of the day you will buy an aftermarket exhaust anyways when considering tuning as a serious hobby :)

Removing the catalyst from the exhaust is much more difficult as the exhaust needs to be cut open and after removal welded together again. Whilst this can be done it is usually not worth the effort.

Some catalyst exhausts have a hose connected to the transmission housing (Piaggio). This hose is needed to keep the catalyst clean. When the catalyst exhaust is being replaced this hose should be removed and the hole in the engine block closed.

Different countries have different laws. Some allow riding a scooter without a drivers license and others have multiple different licenses for various engine sizes. Besides the discussed stock restrictions below there are other restrictions possible that allow you riding a scooter with a drivers license it was originally not designed for. For example here in Germany we have a very popular license class that allows riding 50cc mopeds with the age of 15 already. However the top speed of the vehicle needs to be restricted to 25km/h to be compliant.

These restrictions are usually provided by third parties which means it is not a restriction applied by the manufacturer of the scooter but a kit bought from a company that specialises in restricting scooters to comply with local drivers license laws. The kit mostly contains of an electronically limited CDI and some other parts (removal of the pillion seat, cylinder head spacer to decrease compression, etc). These restrictions are not stock and therefore need to be installed by the vendor of the scooter. This also means that all installed and replaced parts are yours. When buying an already restricted scooter make sure to receive all the parts needed to derestrict the scooter again.

Unlike with the stock restrictions, these custom restrictions are explained in detail in your operating license. This makes it easier to find and remove the restrictions.

Removing restrictions and riding a scooter without having the appropriate drivers license is illegal. There are heavy fines and you might loose your license when get caught or involved in an accident!

These are the most common restrictions applied to scooters nowadays and probably the main reason why you are reading this post. In order to comply with various speed limit laws for scooters the manufacturer needs to ensure that the scooter does not go faster than the allowed speed in the country it is sold. On the other hand the manufacturer wants to build engines that perform well in terms of acceleration. This is often contradictory to the speed limit requirement as fast accelerating scooters also reach high top speeds. In oder to stay within the limits but still have a well performing engine various restrictions are applied to the engine so the scooter can receive its road legal certification.

The following restrictions can be found on pretty much every scooter sold nowadays and can be split into two categories:

What’s meant by “added parts”? These are the good restrictions. By good I mean these can be removed easily without spending a single penny (given the right tools). Examples for these are variomatic rings, exhaust dummy pipes and carburetor opening restrictions.

Restrictions through replaced parts on the other hand can’t be simply removed. They usually require the purchase of an unrestricted part or considerable amount of modification. Examples for these parts are: electronically limited CDIs, diameter restricted inlet manifolds and increased length exhaust manifolds.

Derestricting the scooter will increase performance considerably allowing for a much faster acceleration and also a higher top speed (usually about 75km/h). Fuel consumption usually increases but in some cases can be lower or remains the same.

The exhaust restriction is applied to most scooters and can be easily removed. All that is needed is a little grinder (ideally Dremel, Proxxon, or other micro grinders). Most stock exhaust feature a dummy pipe on the exhaust manifold whereas restricted after market exhausts have a little diameter restriction welded into the down pipe.

In order to remove the dummy pipe simply cut off the pipe with a handsaw or a micro grinder. It should be cut off as close to the manifold as possible. The resulting hole in the exhaust needs to be closed. Welding a washer onto the hole should do the job. Alternatively it is also possible to buy unrestricted exhaust manifolds (e.g. from Piaggio). These are bolt on solutions and cost only about 20-30Euros.

If you want to derestrict in disguise you can weld the dummy pipe back onto the exhaust on top of the washer :)

The diameter restriction is often found on street legal after market exhausts (Stage6 Replica, Yasuni Z, LeoVince, Tecnigas, etc.). Removing the restriction does not require any welding. Simply grind off the small welding spot that hold the restriction in place and it can be easily removed.

To avoid that the restriction piece falls into the manifold when grinding you should build a hook out of some wire and secure its position.

There are some other exhaust restrictions. For example some stock exhausts use a very long exhaust manifold that decreases the gas flow and therefore resulting in reduced performance. These can only be replaced by buying a shortened exhaust manifold.

Another exhaust restriction can sometimes be found in the exhaust silencer of aftermarket exhausts (Yasuni). It can be removed when disassembling the silencer.






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