Do-it-yourself scooter muffler repair

During the operation of the scooter, residues of fuel and oil combustion gradually accumulate in the exhaust system, which leads to noticeable deterioration in operation, whether it is a two-stroke or four-stroke engine.

An exhaust system clogged with carbon deposits can cause a decrease in engine power, interruptions in operation, and excessive fuel consumption. When driving with a sharp opening of the throttle, the engine responds very slowly and the acceleration of the scooter is very weak.

The exhaust pipes of two-stroke engines are more susceptible to carbon fouling than four-stroke engines, although it is on two-stroke engines that this problem more affects the operation of the engine. The engine chokes with its exhaust gases.

It can be quite simple to identify contamination, you need to dismantle the part and blow into the inlet pipe. If at the same time resistance to air flow is felt, then it is necessary to clean it. There are several cleaning methods that differ in their efficiency and labor intensity.

The most radical, at the same time, the most laborious method, which gives the best result, is cutting, and removal of carbon deposits with various scrapers and tools, and subsequent welding by welding. In this case, you need to know the internal structure of the system. Usually, a rectangular window is cut from the side, through which the work is carried out. After the muffler has been welded, it will have to be painted to restore the aesthetic appearance.

It is easier to remove carbon deposits with a wire rope. You need to take a piece of cable of the required length, clamp one end of it into the chuck of an electric drill, and fluff the other, and gradually move it inward, turning the cable with a drill at low speed. In some cases, a positive result is obtained.

Can be chemically cleaned. This method is considered more effective in comparison with the use of a cable. As a cleaning "chemistry" you need to take a household sewer pipe cleaner, such as "Mister Muscle", "Cat" or another similar alkaline-based cleaner.

By the way, the efficiency of exhaust pipe cleaning depends on the quality product used.

First, plug one end of the exhaust pipe, ensure tightness, then pour powder into the muffler, fill it with hot water, and leave it that way for a day.

The next day, pour out all the "dirt" along with the cleaning compound and rinse well with running water from a hose. Then dry and install on the scooter.

The next cleaning method can be called thermal, that is, calcined with a blowtorch or just in a fire. It should get warm, which is called "red hot". You can direct the lamp flame into the exhaust system. Do this until the smoke from the burned-out residues ceases to be emitted.

After such firing, shake out all the carbon deposits, blow it with compressed air from the compressor, and paint it with heat-resistant paint.

We hope that at least one of the above cleaning methods will help restore the exhaust system to work. Increase engine power and quality of work accordingly.

The photo shows the original muffler on the Honda ZX 34/35, namely, its appearance and structure from the inside. The numbers indicate the sequence of passage of exhaust gases through the pipes from one chamber to another. Tube # 4 is the longest on it most of all burns are formed, and most often this tube is the cause of a clogged muffler.

Muffler design Honda Lead 50/90 (AF20E / HF05E) Read more →

Do you need a forward flow on a scooter?

Direct flow mufflers are well known in the world of automotive and motorcycle tuning. Is it possible, and most importantly, is it necessary to use "forward flow" on scooters? Let's figure it out. Continue reading →

Normal combustion of the air / fuel mixture in the cylinder takes place in a precisely defined process. Ignition begins with a spark from the spark plug shortly before reaching top dead center. The flame spreads in a circle from the spark plug and passes through the combustion chamber at a constantly increasing combustion speed of 5 to 30 m / s. As a result, the pressure in the combustion chamber rises sharply and reaches its maximum value just after the top dead center. To reduce the load on the parts of the crank mechanism, the rate of pressure rise per degree of crankshaft angle should not exceed 3.5 bar. This normal ignition process can, however, be disturbed by various influences, which can be summarized mainly in the form of three completely different cases of combustion disturbances:

1.Glow ignition (premature ignition): this leads to a thermal overload of the piston

2. Knocking ignition: it leads to erosive material removal and mechanical overload on the piston and crank mechanism

3.Fuel overflow: this leads to wear with excessive oil consumption and also piston seizure. Continue reading →

Many people immediately start sounding the alarm:

- "Rings sat down, oil takes from the crankcase!" - what nafig rings. Which crankcase is the oil. On a two-stroke.

- "AAA! The oil pump must be regulated!" - Kaaak. I have not seen a single pump in my practice with adjustments! Just don’t shout about the oil pump cable. They are not adjusting. No, it certainly regulates the flow, but they do not regulate anything, it only needs to be set to the “0” position once.

If a 50cc motor consumes about a liter per thousand kilometers and is not killed and feels great, but at the same time it has a “wet end”, this only means that the oil does not burn in the cylinder. In general, ideally, it should not burn, it should lubricate. This is usually found in those who drive calmly and not scalded. Continue reading →

What is a muffler and what is it for? The goal is to acquaint you not only with how to design a homemade scooter muffler with your own hands, but also with what the purpose of this important unit is.

A scooter, as you know, can be with a two-stroke or a four-stroke engine. The principle of operation of the entire exhaust system for analogs is fundamentally different.

A muffler on a four-stroke scooter removes gases in a relatively shorter time, doing so with minimal noise. In addition, tuning the muffler in this case will be quite simple. On the other hand, in both cases, when carrying out tuning, it will be necessary to change the pipes.

Types of mufflers on a scooter

For a muffler of a two-stroke scooter, it will be much more difficult to select components that make it possible to carry out tuning. The regular muffler for such scooters is more difficult to manufacture and configure.

The exhaust system of a two-stroke scooter works as follows. During the exhaust gas cleaning process, some of the power is returned to the engine. This happens at certain speeds and if you manage to implement this whole process, after tuning, the scooter will not be recognized.

You can install a high-quality and properly tuned resonator on a two-stroke scooter. This will give a noticeable increase in dynamics up to a quarter. But in this case, it will be relevant to carry out professional settings for the entire power system.

As you know, a certain amount of fuel combustion products is collected in the cylinders of a moped engine. They must be thrown away, and in this case it is the muffler that is responsible for this.In other words, this unit, as it were, smooths out the pulsations that are inevitable when exhausting combustion products at high speed.

The very design of the muffler, which is used not only on scooters and mopeds, but also on motorcycles and cars, implies a special exhaust system, which may be different, depending on what result the vehicle owner wants to get. For example, if the desire to improve the gas outlet system is associated with an increase in the power of the scooter, a special type of muffler is needed - a direct-flow one.

Direct flow muffler device for moped

Installation of this type of muffler will entail not only an increase in dynamic power, but also significantly increase the noise emitted when gases are emitted. On the one hand, this is good, because this way you can attract the attention of other drivers, thereby increasing passive safety. As you know, drivers of large cars often complain that they do not notice motorcyclists, and even mopeds and scooters, even more so.

It is not difficult to make such a muffler from scratch or with a tuning method, but there are many technical aspects to be learned.

The features of the direct flow are as follows: exhaust gases are thrown out of the engine immediately, the cylinders of the power unit have time to be filled with the fuel mixture in the optimal amount.

I would like to remind all readers that at the moments of intake and exhaust, engine valves tend to open and close. Between these stages, a vacuum occurs, which allows you to clean the cylinders of exhaust gases. As a result, free space is freed up, where the fuel mixture is supplied. It is easy to guess that the faster the cylinders are freed from the development, the faster they will fill.

Thus, if you can ensure a faster escape of gases from the system, the productivity and, as a result, the power of the scooter or moped will increase.

The cleanliness of the muffler affects the performance of the moped

Before starting to change anything in the exhaust system, I would like to give one piece of advice. The power of the scooter is directly affected by the cleanliness of the muffler. If it was possible to see the working off in the cut of the muffler, the owner of the scooter would be very surprised. After a certain mileage, the dynamics of the scooter decreases, and the owners begin to look for the reasons for this, finding them in a complete alteration of the standard muffler or its replacement.

The reason for the loss of power, however, may be hidden in the state of the engine itself. This will help determine the specialist who should be contacted before tuning. But the most common reason for the loss of dynamics is soot, which clogs the muffler. Cleaning in this case is recommended in three ways.

It involves cleaning in the cut of the muffler (it is done with a grinder). The inside of the muffler is cleaned from soot with a wire or cable. The section is closed by welding.

It means pouring water with some kind of purifier into the muffler. For example, caustic soda is suitable for this purpose. There is an advantage with such cleaning: the appearance of the muffler will not be affected in any way.

The muffler is heated either on a scooter with a blowtorch, or dismantled in a furnace or on a grill. It will be necessary to repaint the muffler only after cooling down.

As a rule, many craftsmen do not just assemble a muffler, but alter a regular one. This makes it possible to spend less time and get a more acceptable option.

Before you start tuning, you need to prepare the necessary tools. In this case, the following components will be needed:

1. Welding machine, preferably with different operating modes;
2. Pipe of appropriate size and diameter;
3. Bulgarian;
4. Metal dishwashing brushes in the amount of several pieces.

First, we dismantle the muffler. Then we take a grinder and cut out a piece of metal on top of the muffler. In such a cut, it will be much easier to work with a muffler. You should almost completely cut out the top.After that, it is necessary to clean the entire inner space of the muffler, carrying out the dismantling of the elements that are in the cut.

It's time to work with the pipe segment that we have prepared. Using a powerful drill or welding, we make many holes in the pipe. We place the pipe in the cut of the standard muffler. We select in advance a pipe of such a diameter so that it fits inside the standard one. It is desirable that the pipe be free of any obvious flaws and perfectly flat.

Direct flow muffler during assembly

The space in the cut that remains between the two pipes must be filled with metal brushes or similar materials. We weld the top of the pipe, as it was. We mount back all structural elements that were dismantled in the process.

As a result, which gave the tuning, we get a forward flow muffler, providing the desired result. The massive and luscious roar of the engine, as well as the increase in the power of the moped, will be evidence that everything went well.

You can make such a muffler from scratch. It will be a completely new variant made from several components. The tricky part of this operation, called tuning from scratch, is finding the exhaust system for a particular moped.

In this case, again, you need to prepare the necessary tools and materials.

1. Purchase from a store or find two pipes with a diameter of 33 mm;
2. Buy plexiglass;
3. Bolts М8 and М3;
4. We prepare glue and nails;
5. Welding machine;
6. Needle files;
7. Hacksaw for metal.

First of all, you need to cut 18 cm from one of the pipes. It is recommended to carefully process the place in the cut with a file. Cut a circle from the second pipe with a diameter of 1.5 cm. We process it using the above method. We glue the cut out circle in the cut of the first pipe. We cut off another piece of pipe, 18 cm long. We make many holes in it. This can also be done with a sharp nail.

We connect all the parts using a welding machine. We fill the cavity formed at the junction of two pieces of pipe with mineral wool. We wrap the finished product with a special fire-resistant material. The homemade muffler is ready. To install it, you will need to attach the element to the attachment of the scooter body.

From plexiglass, which is indispensable in this matter in view of its strength and easy coloring, we cut out a special type of ring, the edges of which can be bent outward by 180 degrees. We attach the resulting circles with serifs to the moped, using the bolts needed. We polish the muffler with sandpaper. The joints of the homemade product with the body of the moped will need to be lubricated for fidelity.

Disassembled homemade muffler for moped

If homemade production causes certain difficulties, you can find a lot of models of mufflers already ready-made. They are usually inexpensive. On the other hand, only a home-made version is able to give the perfectly expected version.

If the scooter gradually loses power, and everything is in order with the carburetor, cylinder and transmission, then it's time to check the muffler for clogging. Since oil is constantly burning in two-stroke engines, it is not surprising that sooner or later the muffler becomes clogged with carbon deposits. And soot can reach such a thickness that it will significantly reduce the diameter of the passage holes inside the muffler. The exhaust system will not be able to work properly and the engine power will drop.

Therefore, it makes sense to occasionally check the muffler for clogging. How often to do this, I do not know - probably not more often than once every 5000 km. To check, you need to remove the muffler and blow into its pipe, previously wrapped with a napkin. If the air flows with resistance, then the muffler is clogged.

There are 3 main ways to clean a muffler:

• chemical, e.g. with alkali or solvent
• burning from the outside, for example, in a fire
• cutting, burning and reverse brewing drank

I don't have a welding machine, so the third method disappears automatically. And in general, sawing, burning, boiling, then painting - it's easier and cheaper to buy a new muffler, I don't see any point in doing this kind of work. The second method, with burning in a fire and percussion, does not require a welding machine, however, the muffler will still be disfigured externally, and this is also not my option. After all, I am a lover of chemistry, and my muffler is not clogged enough to proceed to drastic measures. So, we clean with chemistry!

For cleaning, you will need alkali - caustic soda, it is also caustic soda. It can be purchased as a clogged pipe cleaner "Mole" for just over 8 rubles. I took 2 sachets.

In order to remove the muffler, we need a 10 and 12 socket wrench.

First you need to open the seat and use a 10 key to unscrew the 4 bolts securing the seat to the frame. On the Honda Tact scooter, you will need to unscrew and remove the oil tank cover. After unscrewing the bolts, remove the seat.

Now you need to loosen the two nuts securing the muffler to the cylinder. It is not necessary to unscrew them to the end, it is enough to unscrew them by about 5-6 mm.

Next, using a 12 key, unscrew the bolts securing the muffler to the engine crankcase.

The muffler is removed, you can carry it inside the house.

It is necessary to plug the exhaust hole of the muffler with a rubber stopper.

We fall asleep "Mole" in the muffler. In general, this should be done with rubber gloves. I didn’t realize it right away, so the Mole bit me slightly.

Now fill the muffler with hot water. Carefully! The reaction of dissolving the caustic soda in the water will also add heat, so the muffler will get very hot!

Shake the filled muffler and leave for a day.

It's time to drain the stuff. Well, I have a new muffler, so I didn't see anything terrible at the exit.

After draining, rinse it well from the shower hose. At the same time, the bath turns into a nightmare, so the procedure should be carried out in the absence of household members. Well, or in the presence of those who do not understand anything :). Then you will have to wash the bathtub with Domestos and other cleaning agents for a long time.

After washing, it remains only to shake out all the water from the muffler. And then I immediately dried it with a hairdryer at the lowest temperature. This should be done outdoors as it will smell badly.

So, for just 17 rubles, you can clean the muffler. If you do not start its condition, then the muffler will serve your scooter for a very long time!

Note: This article and the images in it are subject to copyright. Partial or complete reproduction on other resources without consent is prohibited.

Methods for cleaning the scooter muffler from carbon deposits

A clogged muffler significantly reduces engine power and contributes to increased gasoline consumption. A clogged muffler is common on two-stroke scooters.

There are several cleaning methods, from light and ineffective, to heavy, but after which the exhaust pipe is completely cleaned.

The simplest method is wire rope cleaning. We clamp one end into the drill chuck, unfold the other in the form of a ruff, without removing the pipe, gradually move the cable inside the pipe, while slowly turning the cable. If possible, cleaning should be carried out up to the stop of the cable. The method is quite effective. but it does not last long.

A harder method, cleaning the Mister Muscle muffler. This powder is sold in household chemical stores and is intended for cleaning clogged sewers. You will need to remove the muffler for cleaning. The method is effective only with insignificant deposits of carbon deposits in the muffler. Almost never applied.

But this method is already effective. Cleaning the muffler with a blowtorch, gas torch, even over a fire is not important. The main thing is to warm it up to red, tap it gently in a circle with a wooden stick, and be sure to blow out the carbon residue with a compressor. You will not be able to simply pour it out.Then paint with heat resistant paint. The disadvantage of this method is that due to the presence of a refractory element in the shell of the muffler, the inner tubes may not be cleaned well enough.

If all these methods have not worked for you, and the muffler is still clogged, the only method to clean it is by cutting. And then burning it out from the inside. This method is the most difficult, but the effectiveness will not disappoint you.

Learn more about each cleaning method in the following articles.

You can also check out other articles on the topic:

During the operation of the scooter, residues of fuel and oil combustion gradually accumulate in the exhaust system, which leads to noticeable deterioration in operation, whether it is a two-stroke or four-stroke engine.

An exhaust system clogged with carbon deposits can cause a decrease in engine power, interruptions in operation, and excessive fuel consumption. When driving with a sharp opening of the throttle, the engine responds very slowly and the acceleration of the scooter is very weak.

The exhaust pipes of two-stroke engines are more susceptible to carbon fouling than four-stroke engines, although it is on two-stroke engines that this problem more affects the operation of the engine. The engine chokes with its exhaust gases.

It can be quite simple to identify contamination, you need to dismantle the part and blow into the inlet pipe. If at the same time resistance to air flow is felt, then it is necessary to clean it. There are several cleaning methods that differ in their efficiency and labor intensity.

The most radical, at the same time, the most laborious method, which gives the best result, is cutting, and removal of carbon deposits with various scrapers and tools, and subsequent welding by welding. In this case, you need to know the internal structure of the system. Usually, a rectangular window is cut from the side, through which the work is carried out. After the muffler has been welded, it will have to be painted to restore the aesthetic appearance.

It is easier to remove carbon deposits with a wire rope. You need to take a piece of cable of the required length, clamp one end of it into the chuck of an electric drill, and fluff the other, and gradually move it inward, turning the cable with a drill at low speed. In some cases, a positive result is obtained.

Can be chemically cleaned. This method is considered more effective in comparison with the use of a cable. As a cleaning "chemistry" you need to take a household cleaning agent for sewer pipes, such as "Mister Muscle", "Cat" or another similar agent on an alkaline basis.

By the way, the efficiency of exhaust pipe cleaning depends on the quality product used.

First, plug one end of the exhaust pipe, ensure tightness, then pour powder into the muffler, fill it with hot water, and leave it that way for a day.

The next day, pour out all the "dirt" along with the cleaning compound and rinse well with running water from a hose. Then dry and install on the scooter.

The next cleaning method can be called thermal, that is, calcined with a blowtorch or just in a fire. It should get warm, which is called "red hot". You can direct the lamp flame into the exhaust system. Do this until the smoke from the burned-out residues ceases to be emitted.

After such firing, shake out all the carbon deposits, blow it with compressed air from the compressor, and paint it with heat-resistant paint.

We hope that at least one of the above cleaning methods will help restore the exhaust system to work. Increase engine power and quality of work accordingly.

How to make a forward flow on a scooter.

Direct flow is a type of high flow exhaust system.

By installing a straight-through muffler, you can increase the power of the vehicle and achieve a noble sound of the engine.

Author Dmitry Konorkin, on the site under the nickname Dima 73.

Therefore, many scooter owners sooner or later have a desire to remove the catalyst from their muffler.

1. - grinder;
2. - drill;
3. - hammer;
4. - mesh or tube with holes (it is possible with notches);
5. - Steel shavings or sponges (metal) for cleaning pots;
6. - heat resistant paint.

1. First, remove the decorative shields and muffler by unscrewing the four bolts. Cut it near the knee in a circle using a grinder or a hacksaw for metal.

2. You now have a choice between two options:

First option leave the old pipe and get all the junk out of it.

Second option find a new pipe, without unnecessary torment.

3. We are looking for stuffing for the muffler, in our case it will be a sponge (metal) for cleaning pots, you can also use glass wool. Glass wool has a big drawback, it gradually burns out and flies out through the pipe, it is also very unhealthy. We do not save on sponges, we buy the densest, 11 pieces were enough for me.

4. "We grab" first the inner pipe, then apply the outer pipe, if everything worked out, then we boil the inner pipe, and only then the outer one. Everything should be level, and the inner pipe is clearly in the middle.

5. We fill the muffler, do not rush, there is no need to tamp the metal shavings.

We push the sponge with a long and wide object.

This is how it should turn out!

6. We weld the mount, having previously installed everything in place.

7. Weld on the back cover. If you want to make the exhaust quieter, weld the plug onto the inner pipe, in this case, do not forget to leave a space between the inner pipe and the rear cover.

8. A creative step, either you paint with fireproof paint or sand the pipe with fine sandpaper.

Author Dmitry Konorkin, on the site under the nickname Dima 73.

If you also want to share your experience, then write about it on EMAIL.

Removing a muffler on a scooter may be necessary for various reasons, for example, when replacing a piston, replacing a tire or tube, replacing brake pads and adjusting the rear brake, and finally, to clean the muffler itself.

The muffler on the scooter is usually attached to the engine with four bolts (some models may have additional fasteners), including two on the side and two on the bottom (to the cylinder). Some of the names of scooter exhaust systems can consist of several components, which are also bolted to each other.

Let's consider step by step how to properly remove a muffler on a scooter:

The installation of the exhaust pipe on the scooter is carried out in the reverse order.

The muffler of a four-stroke scooter performs its direct function - it makes the exhaust sound quieter. The muffler body is a pipe welded from sheet metal. In this case there are partitions with holes, a glass, also made of a sheet of metal with circular holes and a lining of non-combustible material that wraps it (resembles glass wool). Exhaust gases passing through this structure lose speed and temperature. This reduces the exhaust sound. Below are photos of mufflers from two different scooters.

Option one, installed on Reggy scooters and the like

Since the European requirements for the cleanliness of exhaust gases are quite strict (this does not apply to scooters with a cylinder volume of 50 cc or less), this muffler uses a so-called "second" system. I cannot give an exact definition, but after disassembling I realized: the exhaust gases are mixed with clean air, thus the CO content in the exhaust is reduced.

Left: Exhaust pipe, a small hole on it is an opening for fresh air supply to the muffler Right: The rear muffler cover has been cut off.

Left: front muffler cover Right: steel glass with round holes visible

Left: the muffler body is cut lengthwise, the glass and the mineral wool wrapping it are visible. Right: the front cover with the glass welded to it.

Option two, example - Baotian scooter

I will not talk about the models coming to the Russian Federation, but a full-fledged catalyst is installed in the European ones. Purpose - afterburning of gases and gasoline and harmful substances contained in them.

Left and middle: Disassembled muffler Right: Catalyst visible in the photo

For photographs, mufflers damaged in an accident were dismantled. The analysis was carried out for informational purposes.

A muffler for a four-stroke engine produces much less carbon deposits than a muffler for a two-stroke engine. Cleaning the muffler is, in principle, not recommended and unnecessary. I would not advise you to disassemble a normally functioning muffler.

And in this video you can see how you can still make a direct-flow muffler for a scooter with your own hands:

Even with minimal tuning of the scooter, you need to think about installing resonant exhaust... The principle of operation and an overview of saxophones, as such mufflers are popularly called, we will give in another article.

Saxophone resonant muffler - the thing is not cheap and not everyone can afford it. Accordingly, scooters have a desire to save money and make such an exhaust pipe on their own. In this article, you will learn how to make a primitive homemade saxophone using a scooter as an example. Yamaha jog... Why primitive? Because with this method we will not lead resonator calculations (this requires a special program), but just use the drawing of the saxophone muffler.

The drawing shows Saxophone silencer dimensions on Yamaha Jog.

So let's get started. For saxophone making we need metal, approximately 1.2 mm thick. It needs to be cut according to the dimensions indicated in the drawing (you can adjust these dimensions closer to your parameters). In order to accurately bend the metal, we grind a wooden blank according to the size (such a wooden muffler turned out to be such) and already bend steel according to this shape. After careful adjustment of the workpiece, we weld the joints with semi-automatic welding. We clean the part by any available means.

We also bend the muffler and the muffler pipe. On the one hand, we brew completely, and on the other hand, on rivets (to replace the filler, here is glass wool). After welding, we check all the elements for leaks - there should be no gaps, of course.

We grind and paint all the details. In this case muffler painted with powder paint and everything else with simple acrylic paint.

The mountings on the muffler are made of stainless steel.

And here is the result of our painstaking robots - a copy saxophone Tecnigas... Not bad, right?

Looks even better saxophone scooter.

After installing such a muffler, you may need to adjust the scooter carburetor, adjust the transmission as a whole and the engine in general.

One way to clean a muffler without losing its quiet operation

Greetings to you friends on my motorcycle repair channel! My name is Alexander and at the age of 10, having collected the necessary amount of money, without any demand from my parents, I went to the market and bought a carpathian moped, from that time my motorcycle career began. This is not a hobby or work, it is a part of my life. I take a very responsible approach to the repair of motor vehicles and, most importantly, I love the quality in everything. What I can convey to you dear viewers and subscribers.

Video OWN HANDS: Cleaning the muffler of a 2T scooter, method 2 of the channel SashaDalkevich

Video uploaded by SashaDalkevich
Search SashaDalkevich 5 years ago

One way to clean a muffler without losing its quiet operation

Greetings to you friends on my motorcycle repair channel! My name is Alexander and at the age of 10, having collected the necessary amount of money, without any demand from my parents, I went to the market and bought a carpathian moped, from that time my motorcycle career began. This is not a hobby or work, it is a part of my life. I take a very responsible approach to the repair of motor vehicles and, most importantly, I love the quality in everything. What I can convey to you dear viewers and subscribers.

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Muffler device for a four-stroke scooter

Today we'll talk about the structure of the muffler and the need, as well as the possibility of installing a "tuning" one. Immediately I will disappoint you in being able to squeeze out power by using a tuning muffler from well-known manufacturers. Let me explain why. First, a little theory. In a two-stroke engine, the muffler consists of two parts: the resonator and the muffler itself. It is the use of the "correct" resonator that gives an increase in power. Based on the design of a two-stroke engine (read the article "Design and principle of operation of a four-stroke engine"), intake and exhaust in the cylinder occur almost simultaneously. This means that at a certain moment, both the inlet and outlet ports of the cylinder are open. The exhaust gases go out into the exhaust pipe, and then enter the resonator. The fuel mixture takes their place in the cylinder. But since the exhaust ports of the cylinder are open, some of the fuel mixture enters the exhaust pipe. The purpose of the resonator is to reflect the exhaust gases, create a backward wave from them, which will "push" the fuel mixture back into the cylinder and thereby create a higher pressure in the combustion chamber. Of course, it could be written in more detail, using technical terms and quotes from smart books, but in the end this site is about four-stroke scooters.

So, unlike a two-stroke, a four-stroke ICE has intake and exhaust valves that close the intake and exhaust ports. Thus, the necessity and expediency of using the resonator disappears. The same explains the impossibility of achieving significant results by installing a low-resistance muffler or a straight-through muffler. Of course, this will bring a little power, since the resistance provided by the muffler is reduced. Those who want to change the exhaust sound, make it "more sporty" can install such a muffler. But, I repeat, one should not expect significant results.

Device
The muffler of a four-stroke scooter performs its direct function - it makes the exhaust sound quieter. The muffler body is a pipe welded from sheet metal. In this case there are partitions with holes, a glass, also made of a sheet of metal with circular holes and a lining of non-combustible material that wraps it (resembles glass wool). Exhaust gases passing through this structure lose speed and temperature. This reduces the exhaust sound. Below are photos of mufflers from two different scooters.

Option one, installed on Reggy scooters and the like
Since the European requirements for the cleanliness of exhaust gases are quite strict (this does not apply to scooters with a cylinder volume of 50 cc or less), this muffler uses a so-called "second" system. I cannot give an exact definition, but after disassembling I realized: the exhaust gases are mixed with clean air, thus the CO content in the exhaust is reduced.

Left: exhaust pipe, a small hole on it - a hole for fresh air supply to the muffler. Right: Rear muffler cover cut off.

Left: front muffler cover.
Right: A glass of steel with round holes is visible.

Left: the muffler body is cut lengthwise, the glass and the mineral wool wrapping it are visible.
Right: front cover with a glass welded to it.

Option two, example - Baotian scooter
I will not talk about the models coming to the Russian Federation, but a full-fledged catalyst is installed in the European ones.Purpose - afterburning of gases and gasoline and harmful substances contained in them.