How to install a piston on a scooter: removing and installing the piston and rings

Signs of a CPG malfunction

To determine the breakdown of the piston group, you do not need to have complex measuring instruments. It is enough to pay attention to the following symptoms:

the ringing of piston rings is heard;
The scooter does not start on the first try. You have to perform the operation several times to achieve the result;
rapid emptying of the gas tank due to excessive fuel consumption;
noises are heard in the cylinder/motor that were not there;
the vehicle operates unstably at idle speed;
general reduction in power;
sudden shutdown.

Additional signs include too much smoke and lack of resistance when trying to start the scooter's engine. After disassembling (detailed list of actions below) the motor can be seen on the piston cylinder with black traces - this is carbon deposits. This indicates a loose fit of the pistons to the cylinder walls, as a result of which gases constantly escaped from the inside, which reduced the overall pressure.

Old piston with signs of carbon deposits

In the case of a four-stroke engine, the signs of a CPG failure are slightly different:

presence of thick black/blue smoke;
increased oil consumption;
change in power (this indicator can only be determined during diagnostics, since on a 4-stroke engine the change in parameter may not be immediately noticeable);
inability to start the scooter the first time even with a cold engine.

If these problems are observed, it makes sense to disassemble the vehicle in order to reduce repair costs in the future due to malfunctions of other parts caused by the lack of replacement of the CPG.

How to change the piston on a scooter?

Such elements include the piston, which fails quite rarely, but, nevertheless, sometimes requires replacement.

In order to understand how to independently repair the main components, you need to know exactly how to change the piston on a scooter without harming other parts. First of all, you need to know the reasons why you should change this part, namely:

mechanical wear of the piston, in which its service life is completely exhausted;
mechanical wear of the cylinder;
sluggish speed gain;
installation of a more powerful piston.

You should not try to change the piston when the scooter first malfunctions and the overall dynamics of the product deteriorate. Even if it does not start the first time, this is not a reason to replace such a complex part. If the service life of the piston is not exhausted, postpone its replacement until better times.

Responsible approach to piston replacement

Replacing a piston is a rather complicated procedure, but if you know exactly all the upcoming steps, you can achieve good results and still change the piston system yourself. Since the piston is a key component of the system, it is necessary to correctly select the most suitable option for your model, otherwise the scooter will not be able to move. And then, of course, the owner of the vehicle will say: I changed the piston on the scooter - it won’t start, it won’t start, what should I do? To prevent such questions from arising, it is necessary to approach this procedure responsibly or use the services of professional specialists.

There are only two ways to replace the piston:

go to a specialized store that sells original spare parts that fit strictly specific scooter models;
go to any spare parts seller who will find the most suitable option for your scooter model.

The second option, of course, is more risky, but also more economical, since you can buy a truly new suitable part at minimal cost.

Step-by-step instructions for removing a piston on a scooter

Before you begin removing the piston, you need to organize maximum access to it, that is, free it from other parts. First you need to remove the exhaust pipe, which is bolted to the cylinder. After which the engine cooling casing will be visible, which must also be carefully removed by unscrewing the mounting bolts. Next, unscrew the 4 bolts securing the cylinder, remove only the head and gasket. Then remove the entire cylinder. Very often there are cases when the cylinder cannot be pulled out the first time. To do this, you need to knock on it, for example, with a wooden object, moving it from its place. In order for the cylinder piston to come out as high as possible, it is necessary to turn the crankshaft so that it clears the way. After which you can remove all the components of the piston and bearing. When installing a new piston, the entire procedure is performed in reverse order. It is necessary to drop a little oil on the walls of the new cylinder so that the piston goes in without much effort. If you changed the piston on a 2-stroke scooter, you can easily cope with the task of changing the piston on a 4t scooter, since the general procedure is no different. The main thing is to approach the matter responsibly, carefully and slowly. Thus, it is possible to replace the entire piston system as a whole. The standard kit includes: piston, cylinder, rings, pin and all associated gaskets, which also need to be replaced.

As you can see, the correct approach to this procedure does not entail any particular difficulties, so in this case even a beginner can cope. The main thing is to choose the right piston kit for your scooter model.

1000sovetov.ru

Preparation

So that you don’t have green snot later about the fact that the tuning piston does not fit into the crankcase and you were allegedly deceived here - remove the old piston from the engine and measure the hole for the liner with a caliper. If the hole is smaller than the tuning piston sleeve, the “meat” of the crankcase allows it, hands grow from where it is needed - a round file will help you (only before boring - disassemble the engine, assemble the empty crankcase with bolts, bore the hole, make sure that the piston enters the crankcase without problems - wash the parts from shavings and reassemble the engine. Or, as a last resort, coat the crankcase and file with grease to at least somehow protect yourself from sawdust getting into the inside of the engine.)

The hole for the 162QMK engine sleeve (such engines are installed on Chinese scabs, more popularly known as “Leika”) in stock is 65 mm. Without boring, a piston of 57mm (150CC), 61mm (1700CC) and 62mm (180CC) easily fits into this crankcase. You won’t find a 62mm piston on sale during the day, so it was decided to install a regular 61mm piston on this engine.

By the way, for those who do not know, a piston with a diameter of 61 mm can be easily installed not only on the Leica engine, but also on any other Chinese 150 equipped with a 157QMJ series engine. There, if you put your hands to it, you can stick a piston at 62mm, but only if the “meat” of the crankcase allows it. Everything is individual, you need to look at the place. In any case, the distance along the studs is the same for both the 61mm piston and the 62mm piston.

From left to right: 61mm, 57mm

On the 139QMB series engine from a regular Chinese 80-six, you can easily install a piston 39mm (45CC), 47mm (72CC), 50mm (84CC)

From left to right: 39mm (45CC), 47mm (72CC), 50mm (84CC)

Installing piston rings

Remove the set of piston rings from the box. A piston ring set for a Chinese four-stroke scooter usually consists of five items. Three of which are a single assembled oil scraper ring, the other two: upper and lower compression.

A typical set of piston rings looks something like this

Or so

Carefully unpack the kit with perfectly clean hands.

In the kit you will find two of the thinnest rings and one thick corrugated ring (expander) - this will be an assembled oil scraper ring that needs to be installed on the piston first.

We place an expander in the lowest groove of the piston

We place thin oil scraper rings in the same groove - one under the expander, the second on top of the expander

We find the lower and upper compression rings in the kit and install them, respectively, in the middle and upper grooves of the piston - with marks on the side surface to the cylinder head (cylinder head). The lower compression ring differs from the upper one in color (not always) and the shape of the working edge (always). In most kits, the lower compression ring is painted black, and its working edge has a slight bevel.

Photo report: Installing a tuning piston on a Chinese 4T scooter

Installing a piston with a larger volume than stock is perhaps the simplest, most affordable, affordable and effective way to significantly increase the maximum speed and power of a scooter. There are, of course, even more effective ways to increase maximum speed and power, but these methods, or rather the hardware, cost simply unrealistic money...

If you charge the engine of the same 139QMB to the maximum, then such tuning before the “increase” cost the client about 35,000 rubles and this does not include work.

It is clear that not everyone can afford such amounts. Yes, even if it’s affordable, what’s the point? It’s easier to buy an old branded scooter and ride it than to charge the “Chinese” and then throw it in the trash after a season. But that's what I think.

Preparation

From left to right: 61mm, 57mm

On the 139QMB series engine from a regular Chinese 80-six, you can easily install a piston 39mm (45CC), 47mm (72CC), 50mm (84CC)

From left to right: 39mm (45CC), 47mm (72CC), 50mm (84CC)

Installing piston rings

A typical set of piston rings looks something like this

Or so

Carefully unpack the kit with perfectly clean hands.

In the kit you will find two of the thinnest rings and one thick corrugated ring (expander) - this will be an assembled oil scraper ring that needs to be installed on the piston first.

We place an expander in the lowest groove of the piston

We place thin oil scraper rings in the same groove - one under the expander, the second on top of the expander

Piston installation

Insert a retaining ring into any boss of the piston pin. It is most convenient to insert the ring with small round nose pliers. After installation, check how well and tightly the retaining ring fits.

If the retaining ring does not cover the entire surface, but only a small part of it, replace it with a new one.
If the retaining ring does not lie tightly in the groove and dangles, straighten it a little

Lubricate the bearings of the lower and upper connecting rod heads and the piston pin bosses with clean engine oil. We put the piston on the connecting rod, orienting it with the “IN” mark to the inlet port; if there is an “arrow” on the piston instead of the “IN” mark, orient the arrow to the exhaust port. We insert the piston pin into the boss - orient the piston on the connecting rod so that the pin hits the connecting rod - install the pin all the way into the locking ring and secure it from falling out with the second locking ring.

We install the cylinder guide bushings on the studs and put on the gasket. It is advisable to place the gasket on the sealant, but without fanaticism.

Piston ring lock alignment

Place the lower oil scraper ring lock opposite the red arrow
Place the upper oil scraper lock opposite the blue arrow
We place the lock of the lower compression ring opposite the yellow arrow
We place the lock of the upper compression ring opposite the green arrow

Cylinder installation

Fill the rings and piston with clean engine oil. We tighten the piston rings with a clamp. We cut the clamp from a piece of any sheet metal - cut out a strip of the required length, give it a profile along the piston and make a retainer from the same piece of sheet metal.

Lubricate the cylinder mirror with clean engine oil

We hook the timing chain with a piece of wire, pull the chain through the cylinder and put the cylinder on the studs.

Very carefully and slowly insert the piston into the cylinder. After the rings are completely inserted into the cylinder, unfasten the clamp and install the cylinder into the crankcase.

Setting the valve timing ch1 (in collective farm style - ignition)

We push the cylinder all the way into the crankcase and set the piston to top dead center (TDC). It is best to set the piston at TDC using an indicator or, at worst, visually/touch. You can also align the piston according to a special mark on the generator rotor, but I have more than once encountered the fact that the marks on some engines are stamped incorrectly and, in order to avoid troubles, I advise you to use them only as a last resort, for example, when the cylinder head is not removed and you need to adjust valve

We insert the cylinder head guide bushings and the lower timing chain guide into the cylinder, degrease the surface and install the gasket.

We install the cylinder head, insert the valve bed guide bushings.

Setting the valve timing ch2 (in collective farm style - ignition)

Without knocking the piston off from TDC, we orient the camshaft so that the large hole and marks on its sprocket become as shown in the photo and, while putting on the chain, install the camshaft in bed.

Ideally, the marks on the sprocket should be strictly parallel to the plane of the valve cover connector. In practice, unfortunately, such accuracy is difficult to achieve. And this is mainly due to the stretching of the timing chain. And there’s nothing you can do about it - either change the timing chain to a new one or catch the phase by switching the teeth, but this method of setting the valve timing is not acceptable to me personally.

We orient the camshaft bed with a mark in the form of the letters “E” and “X” towards the exhaust channel and install the bed.

Tighten the bed nuts crosswise and then tighten the two bolts on the side boss of the cylinder head.

Installing the timing chain tensioner

If you have a 157QMJ series engine, do the following: unscrew the plug on the tensioner body; We insert a thin flat screwdriver into it and begin to tighten the bolt until the tensioner rod goes inside the body.

Without releasing the screwdriver while simultaneously holding the tensioner body, with your free fingers, insert the tensioner into the cylinder, screw it in with bolts, and only then release the screwdriver and screw the plug into place.

If you have a 139QMB series engine, then do this: unscrew the plug from the tensioner housing and remove the spring; push the rod inside the body; install the tensioner in the cylinder; insert the spring into the housing and screw in the plug.

After installing the piston, do not forget to adjust the thermal clearances of the valves and break in the engine.

alisa-motors.ru

Payment via Yandex Cashier

After selecting payment via Yandex, the Yandex Cashier payment system will launch, where you need to select a convenient payment method (bank card, QIWI, Yandex Money account, etc.)

After specifying payment details and confirming payment, payment for the goods will occur.

If you have a bank card in a currency other than the ruble, then the money will be debited from the card at the rate of the Central Bank of Russia at the time of the purchase.

This payment method is optimal for residents of Russia, Kazakhstan and Belarus.

Official website of the Yandex Kassa payment system https://kassa.yandex.ru

3 comments to “Photo report: Installing a piston on a two-stroke scooter engine”

Here is an excellent video tutorial on installing a piston on a Chinese scooter, everything is very clear and understandable https://moevideo.net/video/30761.39c7166bf284de714a3a743612da

Well, I wouldn't say that everything is so simple. The fact is that a good master will disconnect the engine from the frame and will not struggle like in the video. 1. In the video we see an example on a scooter with a 139 QMI engine and maybe, but on a 152 QMI-157 QMJ such a trick will no longer work, even the cylinder head cover cannot be removed so easily. 2. A normal person (like a good master) will set the TDC on the scooter in advance before replacing the CPG. They even write about it on the Internet. The video is exclusively for real masters; for beginners it will be difficult to “stuff” the piston hanging on the connecting rod with rings into the cylinder. It is not so easy to do as shown in the video. I know for myself that a beginner cannot do this. There is a more humane way, and it is safer than this.

Evgeniy, good rating for the video, I haven’t watched it myself.

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Instructions on how to correctly install the piston on a scooter yourself?

During the operation of the scooter, various breakdowns occur. It doesn’t matter at all who the manufacturer is (Japan or China). The difference is that one vehicle breaks down earlier, while the other breaks down over time. Problems can occur with the wiring, engine, or chassis. But, as a rule, almost everyone is faced with replacing the CPG. This abbreviation implies the term “cylinder-piston group” or, as people say, “piston group”. Looking ahead, it must be said that replacing the piston, piston and rings separately is not as difficult a task as it might seem at first glance. It is also worth knowing that the process of removing and replacing the CPG is almost the same on all scooters. Therefore, the article will discuss the main points. Looking ahead, let us remind you that the power of the CPG can vary. It is recommended to install a piston engine with the same power as a standard CPG.

Preparatory moments

Before replacing the piston or rings (CPG in total), you need to get to the cylinder. For beginners who have no idea where this element is located, we will tell you. The muffler is just bolted to the cylinder. If you have no idea how to correctly install the piston on a 4t or 2t scooter, then first you need to remove the old CPG. The upcoming repairs can be divided into the following stages:

Removing the scooter trim (plastic);
Disconnecting electrical wires;
Disconnect the oil hose;
Engine dismantling;
Removing the old piston, rings (CPG in total);
Installation of new parts;
Engine installation, wire connections and hose;
Plastic fastener.

The plastic is folded to the side so as not to be crushed if careless. All bolts and screws are placed in a pile and, if necessary, sorted separately. After making sure that all hoses with gasoline and oil are disconnected, remove the engine. It is necessary to understand that engine removal differs depending on the design features of the scooter model. Once the engine is removed, you can begin to remove the plastic casing, which protects the CPG from external factors. Then remove the cylinder head. It is secured with 4 bolts. In order not to break the thread, all bolts are unscrewed crosswise.

We remove the cylinder and immediately inspect it. If there is no damage, then it can continue to be used. While the piston most likely cannot be used back.

How to properly install a piston on a scooter

The new piston is equipped with a pin, two retaining rings and additional rings. If the scooter is 2-stroke, then the number of additional rings is 2. In 4-stroke engines, 3 rings are almost always installed, one of which is an oil scraper ring. Let's look at installing a piston and rings using the example of a 2-stroke scooter. First, two compression rings are placed on the piston in special grooves. Next, we use the so-called “finger” to connect the piston and crankshaft; the fastener is considered complete after installing 2 retaining rings on both sides of the finger. The rings should fit tightly in the intended holes. Remember: the arrow on the piston should point downward, towards the floor. The “processes” described above are not complicated if you look at them. It is best to watch a training video or read the scooter maintenance instructions. Then, for sure, questions like “How to install rings on a scooter piston” will not arise.

Cylinder installation

This is the final stage and must be approached with caution. After all, if the fastening is incorrect, the slightest gap will not provide the necessary compression. As a result, the scooter will not start. Install a gasket between the engine and the cylinder, and between the cylinder and its head. The head is clamped with bolted connections crosswise. It is easy to check the correctness of the work performed. To do this, you need to start the engine. If the motor runs smoothly, everything is done correctly. You can also make a few efforts with the kick starter to feel the compression.

As you have already killed yourself, there is nothing complicated. Installing rings on a scooter piston and replacing the CPG in total do not require any special knowledge. All you need are details, time and desire.

topkarting.ru

Piston installation

Insert a retaining ring into any boss of the piston pin. It is most convenient to insert the ring with small round nose pliers. After installation, check how well and tightly the retaining ring fits.

If the retaining ring does not cover the entire surface, but only a small part of it, replace it with a new one.
If the retaining ring does not lie tightly in the groove and dangles, straighten it a little

We install the cylinder guide bushings on the studs and put on the gasket. It is advisable to place the gasket on the sealant, but without fanaticism.

How to put rings on a scooter

It is worth noting that durable and trouble-free operation of the piston largely depends on the correct installation of the rings. There is absolutely no need for haste and dirt in this matter. Do everything carefully (for yourself, after all), slowly and most importantly: keep it clean!

First, let's take a little look at what a standard set of piston rings for a four-stroke scooter engine is. The standard kit consists of: two compression rings (upper and lower) and one oil scraper ring, which in our case has a collapsible design.

A set of piston rings for a two-stroke scooter engine differs from the previous one in the absence of an oil scraper ring; also, a set of rings for a two-stroke engine may include an expander (marked with an arrow).

So, we have more or less figured out the kits - it’s time to get down to business. We prepare in advance small strips of tin or thin plastic, with their help we will put the rings on the piston.

We thoroughly wash the rings and piston; when installing new rings on a used piston, do not forget to clean its grooves from carbon deposits, otherwise the new rings will not fit into the cylinder. We prepare a clean workplace and perform the installation.

We take the oil scraper ring expander from the kit and place it in the lowest groove of the piston.

In the same way, we install the expander from the kit for a two-stroke engine (if any), with the only difference being that the expander lock should be located in the area of the locking pin (marked with an arrow) of the piston groove.

We look for marks on the rings, apply pre-prepared strips to the piston, very carefully and slowly pull the rings along our strips onto the piston, in this order: first we put on the oil scraper ring, then we put on the second oil scraper ring, then we put on the lower compression ring (dark) and only then put on the upper compression ring (light). The marks on the rings after installation should be located upward towards the cylinder head.

We straighten the rings so that they stand exactly opposite their grooves and slowly pull out our strips from under them. Now the main thing: after you have pulled out the strips and the rings are in their grooves without fail, check each ring for mobility. The rings in the piston grooves should rotate freely in different directions.

How to install a piston on a scooter: remove the old one, install a new one

Getting to the piston cylinder will be easy if you follow the instructions. You need to start by removing the plastic lining of the scooter, and then disconnect the wires. The oil hose is disconnected, and the motor itself is removed by unscrewing the fasteners. The plastic cover should be set aside so as not to crush it due to careless movement.

To get to the piston, you ultimately need to remove the cylinder head, and then the cylinder itself.

Dismantling the piston itself is carried out in the following sequence:

remove the CPG mounting bolts along with the head and gasket. Each bolt must be unscrewed in a criss-cross manner (diagonally) to avoid damaging the threads - installing the piston back requires using the same method. This will also prevent unwinding without the participation of the owner;
directly dismantling the cylinder using upward movements - if you can’t pull it out, it is recommended to knock with a light wooden object. The product may become stuck due to the deposits listed above;
turning the crankshaft for maximum piston lift. Be sure to cover the crankcase hole with a rag to prevent dirt from getting inside;
you need to remove the retaining ring in order to remove the piston pin;
In case of jamming, you need to use liquid to remove carbon deposits. An alternative is carburetor cleaner. As a result, after soaking, all plaque is easily removed, similarly with rings;
cleaning ring grooves.

Step-by-step video on how to remove the piston from a scooter:

You will need to inspect the needle bearing for signs of burning, indicating wear of the part. If they are, a change is required immediately. Installation of a new CPG will not be effective for long in the absence of proper care.

Needle bearing

You should also pay attention to the following factors:

if there is displacement of the needles inside the cage, the product as a whole is unusable;
violation of geometry also indicates the need for replacement;
There should not be much play when moving in the upper head of the connecting rod. In normal condition, the bearing simply moves freely.

As a result of changing the needle bearing, you can install a new piston for the scooter. Installation is carried out in reverse order. Several features of the procedure must be taken into account:

Repairs can be carried out using a special kit containing all the necessary tools:

piston ring remover (pliers);
piston groove cleaning device;
L-shaped screwdriver.

All this can be found separately. The main thing is to follow the dimensions that will suit a specific scooter model.

Step by step video on how to install a new piston on a scooter:

How to install a piston on a scooter?

One of the most serious breakdowns of a scooter is the failure of the cylinder-piston group, which immediately makes the scooter inoperative. It is the scooter’s CPG that is responsible for its movement; the slightest breakdown will lead to the impossibility of further movement. That is why if you are faced with a non-working piston, immediately start repairing it.

In general, any CPG has a certain lifespan; with a certain mileage, its wear increases and the buyer will have to replace the part. Often replacing the piston is enough, but sometimes more serious problems occur. Where you have to change the piston, rings and cylinder. Depending on the scooter model and manufacturer, the installation may vary slightly, but we will cover the basic steps. Also, piston scooters may differ in power, but this does not affect the replacement process in any way.

Removing the CPG

If you don't know how to properly install a piston on a 2t or 4t scooter, the first step is to remove the old part. Getting to the piston group is not easy; you will have to disassemble the scooter and sometimes remove the plastic. In general, the steps to replace the CPG are as follows:

Removing the engine, disconnecting the wires;
Removing the old piston;
Installation of a new part according to requirements;
Similar engine assembly and electrical and hose connections.

After you have disconnected all wiring and made sure that the -oil and -gasoline hose are closed, remove the engine. Removing the engine may be different in different scooter models, so act according to the situation. Having received the finished engine, begin to remove the plastic cylinder casing; it protects the CPG from external dirt, dust, etc. The next step is removing the cylinder head. Depending on the type of scooter (2t or 4t) the head may be more complex, 4t scooters also have valves that will then have to be adjusted. But the procedure for removing the head is to unscrew 4 nuts.

Important : the nuts must be unscrewed gradually, using the criss-cross method. That is, as shown in the picture below. Otherwise, you will break the thread and damage the piston. This also applies to the installation of the piston; the nuts are also tightened.

Next you will have to remove the cylinder, in some cases this is problematic due to large carbon deposits or a defect in the piston. If the cylinder is intact, but the piston is faulty, proceed to replacing the piston. How to properly install a piston on a scooter

Replacing a piston involves a number of difficulties, because the piston will come with several other basic parts. In the kit you will find locking rings, a pin and several rings (depending on the scooter - 2t or 4t). In 2-stroke scooters, only two rings are usually installed; they are compression rings; the third thin ring is practically not needed, but we recommend placing it under the lower ring for springing. In the case of 4-stroke mopeds, there are three main rings, two of them are compression rings, the third is an oil scraper ring.

The ring assembly is based on a 2t scooter; it has a simpler design. So, put two rings on the piston, then take your finger and insert it into the crankshaft hole so that the piston is held securely. Be sure to secure the finger with locking rings on both sides, this is necessary so that the finger does not come out during operation. Also, the retaining rings should not stick out; they should fit snugly into the special hole. Important: the piston must be installed with the arrow (or the inscription EX) facing the exhaust pipe, otherwise the whole procedure will be useless. The next step is installing the cylinder on the piston.

Cylinder installation

This procedure is quite complicated, because you need to fit the cylinder onto the piston perfectly. First of all, don’t forget to put gaskets on both sides; they are included with the CPG or can be purchased separately. There are usually two gaskets, one is placed down between the cylinder and the engine, the second is installed between the cylinder and the head. After installing the bottom gasket, try to put the cylinder on so that the rings meet in the groove. To do this, when installing the cylinder, it is enough to press the rings, having previously lubricated the cylinder and piston with oil.

Next, put on the gasket and secure the head with nuts. The nuts must be tightened in a cross pattern. Then check the operation of the piston with a kickstarter; if the installation was successful, the piston should move evenly along the cylinder and have noticeable compression.

That's all, reassemble the scooter in reverse order, connect all the wires and hoses.

Setting the valve timing ch1 (in collective farm style - ignition)

We insert the cylinder head guide bushings and the lower timing chain guide into the cylinder, degrease the surface and install the gasket.

We install the cylinder head, insert the valve bed guide bushings.

What will be needed for replacement?

For such a procedure, it is worth preparing a set of wrenches, a ratchet with socket heads, a torque wrench, a piston ring puller and the set of rings itself.

You may be interested in: Mishlene tires: brand history, popular models

The tool for mounting/dismounting piston rings has a simple design and affordable price. Without this device, the replacement process can turn into an almost impossible task. Of course, in the past, car enthusiasts made do with a couple of screwdrivers. But it is better to have such a tool, otherwise without it you can damage the rings or the piston surface. Moreover, it is always available in auto stores.

How to properly install rings on a two-stroke scooter piston

How to assemble a 4t piston system on a Suzuki Sepia moped

You need to arm yourself with a small syringe (preferably a medical one, its price is very low) and oil. The piston is installed on the scooter in stages.

The bearing is mounted, pre-lubricated with oil.

The cylinder, piston pin, rings and new piston must be washed with gasoline and blown with air from the compressor. Only after this should you begin installing them.

Installation of the rings must be done with great care, since the rings are very fragile and can be damaged. It is better to have several spare rings, since the price of one ring is low.

The motor is being mounted.

The piston itself is put on the connecting rod and the piston pin is inserted, after which the final stopper is installed. After installation, you need to check that the arrow on the piston points towards the muffler.

The cylinder, or rather its inner walls, are lubricated with oil, and a new gasket is put on. The stoppers are carefully matched to the ring locks. Now you need to squeeze the rings and put on the cylinder. The cylinder should fit tightly with some resistance; do not press on it with force; the rings may break. If this does not work, then you need to check the installation of the rings.

The cylinder head is installed and tightened through the gasket. The nuts are tightened crosswise by hand.

The following are installed on the scooter one by one:

filters;
motor;
muffler;
candles;
casings.

All hoses and cables are carefully connected.

Before installing the air filter, it must be dried.

Now you need to start the engine and run in the 4t piston on the scooter. You should not do it at high speeds; this can lead to unpleasant consequences; the moped will have to be repaired again. Since the price of work in a workshop is quite decent, independent replacement of such a part as a piston on a scooter is relevant.

Installing the timing chain tensioner

After installing the piston, do not forget to adjust the thermal clearances of the valves and break in the engine.

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Installing rings on a four-stroke scooter piston

There is nothing complicated about installing rings on the piston of a two-stroke scooter, as well as a four-stroke scooter, and many people know this.
But most scooter riders who have only recently acquired such equipment have no idea how to replace the piston on a scooter, how to correctly install the rings on the piston, where the arrow on the piston should point, and much more. In this lesson, I will tell you how to properly put the rings on the piston and assemble the piston in place. Since we have already talked about four-stroke engines before, here we will talk only about two-stroke engines. So, our piston is worn out and requires replacement. The rings and piston wear out first, and usually only those need to be replaced. If the piston is severely worn, it is necessary to bore the cylinder. It is also bored when the piston jams in the cylinder, forming deep scratches on the walls of the latter. There's nothing wrong with that, and if your new cylinder has been properly bored (for which you'll only need to shell out about $10), it will need a ring repair kit with a new piston. Such rings are marked 0.25. The second boring is 0.5, respectively, etc. to one. After purchasing a piston, it needs to be assembled. In the kit, as a rule, you will find the piston itself, two compression rings, a third thin corrugated ring (more on its purpose later), a piston pin and two piston pin retaining rings.

Now about the third ring in the set. Its purpose is to spring the lower compression ring. It installs it directly under it, and usually does not provide any benefit during operation. You can throw this ring away or you can put it in, it makes no difference. Many piston manufacturers do not include it at all.

It's time to put everything back in place. Depending on the scooter model, compression rings may be the same or vary in thickness and cross-section. Most pistons for Honda scooters, for example, have different rings, where the upper one is thinner than the lower one and has a different cross-section.

You should definitely pay attention to this when installing; the top one is thinner and ground at an angle.

Also pay attention to the inscription on the ring (usually the letter T or repair size); the inscription should always be on top, that is, opposite to the finger. First you need to put on the bottom, then the top. There is no need to stretch or bend them. These manipulations must be carried out carefully.

There are locks in the grooves for the rings that prevent the rings from turning during operation, so the ring gap must be in these locks, otherwise you will not stick the piston into the cylinder.

And the last important point is the arrow (1) on the bottom of the piston or the inscription EX. Both the arrow and the inscription must be directed towards the exhaust (2). In this case, the ring locks will be located on the side of the reed valve. If the locks are placed towards the exhaust, the piston will not last long, the rings will be pulled into the exhaust port and gradually grind it down.

During all manipulations with the piston, it is imperative to put a rag in the crankcase window so that nothing inadvertently gets in there; we still need a crankshaft with bearings.

When installing the piston pin, pay attention to the condition of the separator (bearing); it may need to be replaced. Before installing the piston pin, install the snap ring on one side before installing the piston (usually on the side where you won't be able to fit the pin and the second snap ring in). Then place the pin with the bearing and the second retaining ring; when fixed in the groove, it will make a certain click.

That's all, now put on the cylinder, not the piston (remembering to check the condition of the gaskets and lubricate the piston and cylinder walls with engine oil), the cylinder head and tighten the bolts one by one in a cross pattern.

If you have any questions during the piston replacement process, you can ask them in the comments field or on the forum of our website. Good luck with the repair.