How do you de restrict a sports exhaust system?

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Derestricting a sports exhaust system on a scooter

De restrict a sports exhaust system step 1

Even though you maybe purchasing a sports exhaust system designed to improve engine performance and speed, most road legal or E-marked system are supplied restricted so they can be sold in the UK to riders that are only permitted to reach speeds of 30mph. Below we are going to show you where the restrictions are on each brand and also how to remove them.

The most common restriction is found in the manifold end of the exhaust where it bolts up to the cylinder. It is usually a small washer or cone that reduces the diameter of the pipe and can be held in place by one or two small spot welds. Above you can see a selection of restrictions from different brands, all of them do the same job which is to reduce gas flow but they do differ in their appearance.

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De restrict a sports exhaust system step 2

The correct way “we think” to remove this type of restriction is with a dremel or a drill. You need to remove the weld allowing you to slide the cone or washer out, once removed the pipe can operate properly with its intended diameter. We find spraying WD40 around the restriction can make life much easier allowing the restriction to slide out, it’s worth noting that preventing the restriction from sliding down into the expansion can save a big headache, we tend to use a spring hook.

De restrict a sports exhaust system step 3

Each manufacturer has an idea that they may be removed once purchased so they usually come out quite easily. In some cases people remove them by inserting a screw driver into the centre of the restrictor and moving it from side to side breaking the weld, we cannot advise you to use this method as it may damage your exhaust system.

The second restrictor (if your exhaust has two) may be found in the silencer. Depending on the brand this could be at either end of the silencer.

De restrict a sports exhaust system step 4

Some silencer restrictions can be found in the very end of the gas exit pipe where it curls around which is visible externally. Using a small grinding tool to remove the spot weld will release the cone.

De restrict a sports exhaust system step 5

Other brands put them at the end of the baffle tube as shown above. Use the same method we mentioned to remove the manifold washer.

De restrict a sports exhaust system step 6

The likes of Doppler and Artek actually insert a separate component which heavily restricts the system for the European market in the form of a disc with a tube attached, this can be removed easily without the need for any cutting or grinding, simply remove it with your fingers.

Below is a guide as to which make and model of exhaust system has which restriction. Please note this is just a guide, some brands like Giannelli etc are inconsistent at restricting their systems so please check yours:

Doppler S3R – silencer & manifold
Doppler RR7 – silencer & manifold
Doppler WR7 / ER1 etc – manifold & silencer
Giannelli Go – manifold
Giannelli Smile - manifold
Giannelli Extra – manifold
Giannelli Next – manifold
Giannelli Reverse – manifold
Giannelli Shot – manifold
Giannelli Shot V2 - manifold
Giannelli moped systems – manifold
Leo Vince TT – manifold
Leo Vince ZX – manifold
Leo Vince ZXR – manifold
Leo Vince V6 - manifold
Metrakit MK – manifold
PedMoto Series 1 – none
PedMoto SG-1 - none
Polini Team – manifold & silencer
Polini For Race – manifold & silencer
Tecnigas Silent Pro – manifold
Tecnigas Silent Sport – manifold
Tecnigas Proma - silencer
Tecnigas E-box – manifold
Tecnigas G-box – manifold
Tecnigas Enox – manifold
Tecnigas Next R – manifold
Tecnigas Trek – manifold
Tecnigas Q-Tre – manifold
Tecnigas RS ll – manifold & reverse tube
Yasuni Z – manifold & silencer
Yasuni R – manifold & silencer
Yasuni City R – manifold & silencer
Yasuni City C16 – manifold & silencer