Do-it-yourself 4-stroke scooter repair

In order for the engine of a four-stroke scooter to work perfectly, you need only three things: spark, fuel and compression. When troubleshooting, the following rule should be followed - everything is checked gradually, starting from the most elementary faults and ending with the repair of the main parts of the moped.

The first thing to check is the presence of fuel in the tank and in the system. Then check for spark. The engine will not start if the quality of the mixture is broken, or if the carburetor is clogged.

If the ignition key is not turned, the fuse is blown, or the battery is dead, the engine will not show signs of life. Therefore, before proceeding to a global repair, you should check these reasons.

The starter turns over, but the engine does not start.

Possible reasons - a broken candle, a clogged carburetor, no fuel enters the system.

The engine runs erratically or there is a loss of power.

This may indicate that the carburetor is clogged, the oil or air filter is clogged, the head valves are misaligned, the variator or piston group is worn out.

There was a specific knock in the engine during operation.

This may be a sign that the bearings have failed and need to be replaced. It may also be due to the need to adjust the valve clearance.

1. We remove the engine from the scooter. We install the scooter as stable as possible. We remove the trunk. We disconnect all wires from the engine and the gas cable from the carburetor. Remove the fuel hose and vacuum filter. Disconnect the rear shock absorber. After the engine is separated from the frame, unscrew the nut on the mounting axis and remove the axis. After removing the engine, it is advisable to wash it.
2. Removing the cylinder head. It is necessary to carry out to clean the chamber from soot. In order to remove the head, you must first disconnect all the "extra" parts. Then the chain tensioner bolt and locking bolts are unscrewed. Then we turn the flywheel until the T designation matches the one on the engine housing. We unscrew the bolts on which the cylinder is attached and remove the chain, and then the cylinder head itself.
3. Adjustment of valve clearances must be made if a metallic knock appears. The principle of operation is as follows: the cover of the valve mechanism is removed. The mark on the flywheel corresponds to the mark on the engine case. We measure the gap between the adjusting screw and the valve stem. With an increase or decrease in the gap, we adjust by turning the screw.

As practice shows, it is better to entrust the overhaul of the engine to professionals, since there are many nuances that the average driver does not pay attention to, but which in the future can create even bigger problems and then more expensive repairs will be required.
A video about repairing a 4-stroke scooter will introduce you to the main aspects of repair.

A list of the most common scooter problems that you can fix yourself without the help of specialists.
Crime: the brake light does not light, the brake lever limit switch does not work.
Analytics: one of the brakes is not pressed or there is a malfunction in the brake light circuit.
Action: Replace bulb, adjust brake lever free play, or replace brake lever limit switch.

Crime: blown fuse.
Action: Check and, if necessary, replace the main and starter fuses.

Crime: the junction of the terminal with the wire is covered with a loose coating of oxides.
Analytics: The battery is not producing enough voltage, which can be due to a fault in the circuit or if the battery terminals are oxidized.
Action: check the circuit, recharge the battery if necessary. Clean the terminals from oxides.
A temporary measure is to start the engine with a kick starter.

Crime: you turned on the ignition, pressed the brake lever and the starter button, and the starter relay still does not click.
Analytics: Faulty electric starter circuit.
Actions: clean the contacts on the relay and starter, “ring out” the relay, wiring, starter windings.

Crime: when you press the kick starter lever, it scrolls, but the engine crankshaft does not rotate; the leg does not feel resistance to the movement of the kick starter lever.
Analytics: Kick starter or ratchet gear teeth broke. Action: Replace defective parts.
Crime: the electric starter turns the crankshaft, but the engine does not start.
Analytics: the carburetor is “dry” (unscrew the drain screw of the float chamber - you will see). Variants of reasons: the fuel valve filter is clogged, the gas valve is faulty, the fuel line is clogged, the gas valve control vacuum hose has jumped off or is leaky.
Actions: clean the fuel valve filter, blow out the fuel line, make sure that the automatic fuel valve is working.

Crime: fuel is supplied to the carburetor, but does not enter the pop-up chamber.
Analytics: Fuel float valve sticking.
Action: Remove the float chamber cover and clean the valve seat. If that doesn't work, replace the valve.

Crime: you unscrewed the candle, and it is “wet” - covered with a layer of unburned benzo mixture.
Analytics: Excessively rich fuel mixture, which is due to too high a level of fuel in the float chamber or due to a clogged air filter.
Actions: after disassembling the carburetor, check the fuel level, clean the air filter.
Side effects: the engine starts immediately if you splash a little gasoline inside the air filter.
Analytics: automatic start-up enricher does not work.
Action: check the health of the starting enricher (there are several ways - they are described in detail in the repair manuals)

Crime: a spark plug unscrewed from its socket does not spark (in a position where the metal part of the spark plug is in reliable contact with the scooter ground).
Analytics: faulty spark plug: broken insulator or electrodes covered with a thick layer of soot.
Action: clean the spark plug with sandpaper or replace. If a spark still does not appear, diagnose other elements of the ignition system.

Crime: a spark is formed on the spark plug, but weak or “running”.
Analytics: the insulator is broken at the spark plug.
Action: Replace spark plug.

2. ENGINE IS DIFFICULT TO START, RUNS UNSTABLE
Crime: the motor does not “spin up”, pops are heard in the carburetor.
Analytics: excessively lean combustible mixture, a possible cause is sucking air through a loose intake pipe or damaged crankshaft oil seals. Water in the float chamber.
Action: replace the gasket under the pipe and evenly tighten the bolts of its fastening. Replace crankshaft seals. Get rid of the water in the float chamber (by unscrewing the drain screw of the float chamber), blow out the jets and carburetor channels, replace the gasoline in the tank.

Crime: a spark on an unscrewed spark plug (in a position where its metal part is in reliable contact with the "mass" of the scooter) is formed, but the surfaces of the insulator and electrodes are dry.
Analytics: automatic starting enricher does not work (if the engine is cold). A normal combustible mixture is not formed. Clogged idle jet.
Actions: check the serviceability of the starting enricher (see point 1). Blow out the jet and carburetor passages.

Crime: on the insulator and electrodes of the unscrewed spark plug, there are drops of water. Analytics: water infiltrated gasoline.
Action: get rid of the water in the float chamber.

Crime: a spark on an unscrewed spark plug (in a position where its metal part is in reliable contact with the "mass" of the scooter) is formed, but the surfaces of the insulator and the electrodes are covered with black oily soot (photo 5).
Analytics: the brand of the spark plug does not correspond to the thermal regime of the engine - its glow number is higher than that required for this engine (the spark plug is “cold”). The temperature in the working area of ​​the candle is insufficient for self-cleaning of the electrodes.
Action: replace the spark plug with a “hotter” one (with a lower glow number).

Crime: the engine starts normally, but soon there are interruptions in its operation and it stalls.
Analytics: the vent hole in the fuel tank cap is clogged or the hoses responsible for communicating the contents of the gas tank with the atmosphere are clogged.
Action: Clean the vent hole in the fuel tank cap or the hoses.

Crime: when you press the kickstarter lever, there is no resistance to the compression of gases in the cylinder.
Analytics: extremely worn piston, cylinder, piston rings.
Actions: check compression - using a compression gauge or by measuring parts (after dismantling the cylinder). When the diagnosis is confirmed, the engine requires repair with the replacement of worn parts.

Crime: the sound of bursting gases is heard, oily traces form on the head and cylinder.
Analytics: Damaged cylinder head gasket or loose head to cylinder.
Action: replace the gasket and tighten the nuts securing the head to the cylinder with the required torque (force) in the order recommended by the repair manual.

3. ANOTHER SOUNDS IN THE ENGINE
Analytics, version 1: increased wear of parts of the cylinder-piston group.
Action: The engine requires repair with the replacement of worn parts.
Version 2: the thermal gap in the valve drive is violated (for 4-stroke engines).
Action: Adjust valves.
Version 3: the chain in the valve drive has loosened (for 4-stroke engines).
Action: Adjust chain tension.
Version 4: grooves have developed in the variator pulley, along which the rollers move, as well as the rollers themselves.
Actions: replace the worn pulley, rollers (possibly other parts of the variator).

4. ENGINE STOPS WHEN THROTTLE IS OPENED SUDDENLY
Circumstance 1: The engine has just been started.
Analysis: engine not warm enough.
Action: continue warming up the engine at idle.

Circumstance 2: The engine is well warmed up.
Analytics, version 1: the carburetor is not adjusted.
Action: adjust the idle speed, if necessary - the main metering system (see paragraph 5).
Version 2: the variator does not work correctly.
Actions: see point 10.

5. ENGINE STARTS NORMALLY BUT IT DOES NOT SPIN
Crime: thick exhaust smoke, excessive fuel consumption, black deposits on the spark plug electrodes.
Analytics: The main dosing system is preparing an excessively rich mixture.
Actions: adjust the quality of the mixture - lower the carburetor throttle adjustment needle one division (groove) down. It may be necessary to install a main fuel jet with a smaller bore.

Crime: the engine overheats, detonation is heard during acceleration, there is a white coating on the electrodes and the spark plug insulator. After turning off the ignition, the engine continues to run for several seconds (detonates).
Analytics: Carburetor's main metering system is leaning too lean.
Actions: adjust the quality of the mixture - raise the carburetor throttle adjustment needle one notch up.It may be necessary to install a large bore main jet.

Crime: the engine runs unusually quietly (although it starts easily), low-smoke exhaust, the engine “does not pull” during acceleration.
Analytics: muffler, channels and cylinder windows clogged with soot (in two-stroke engines).
Action: if possible, clean the carbon deposits. If the muffler is completely clogged (air does not pass), replace the muffler.

6. ENGINE LOSES POWER AFTER LONG DRIVING
Circumstance 1: The engine is air-cooled.

Crime: the movement of air from under the cylinder casing is not felt, and a sheet of paper does not “stick” to the air intake grid (on the right side of the motor) (if you test with paper).
Analytics: the fan blades are broken, another assumption is that the cooling system casings do not fit snugly or are split in places.
Action: Replace the impeller and damaged casings.

Circumstance 2: liquid-cooled engine.
Crime: coolant is leaking, its level has dropped in the tank.
Analytics: system components are faulty: pump, thermostat, radiator.
Action: replace faulty nodes.

7. THE ENGINE DOES NOT ACCELERATE THE SCOOTER TO 50 KM/H
Inspection data: the speedometer is calibrated, the power or speed limiter is not installed.
Analytics version 1: the design of the scooter is not designed for such speed.
Actions: All actions are meaningless.
Version 2: the carburetor is incorrectly adjusted, the muffler is clogged, or the parts of the cylinder-piston group are worn out.
Action: see point 2 or change the scooter.
Version 3: the variator does not work correctly.
Actions: see p.p. 9, 10.

8. SCOOTER DOES NOT START WHEN ENGINE IS RUNNING
Crime: the variator is faulty.
Analytics: the spring of the driven pulley is broken, the V-belt is broken (to verify this, remove the variator cover - breakdowns are perceived at a visual level).
Action: Replace defective parts.

Crime: faulty centrifugal clutch.
Analytics: shoe springs are broken, shoe linings are excessively worn (it is found out during visual inspection after removing the variator cover) (photo 9). Action: Replace defective parts.

9. SCOOTER JERKS
Crime: jerks are felt when driving.
Analytics: CVT belt slipping (due to wear, damage or oiling) or excessively worn pulley surfaces.
Action: replace defective parts (photo 10).

10. SCOOTER ACCELERATES SLOWLY, RIDES SLOWLY
Analytics: During a recent tuning, the weights of the centrifugal governor or the spring of the driven pulley were not chosen correctly. Centrifugal clutch shoe springs are broken or have lost stiffness, centrifugal clutch shoe linings are worn or oily.
Action: carry out tuning more carefully, preferably with the participation of specialists.

Let's start with the basics of technical inspection

Although four-stroke scooters are more resourceful than two-stroke ones, they, like any equipment, need timely maintenance (TO) at the company's service stations. This will not only ensure long trouble-free operation, but is a condition for the seller to comply with the warranty obligations. However, after the expiration of the warranty period or the desire of the owner, he can carry out all the work on his own. The main maintenance work on the mechanisms and systems of the scooter engine includes: changing the oil and cleaning (replacing) the oil filter, cleaning the air filter, replacing the fuel filter, cleaning and adjusting the carburetor, cleaning carbon deposits from the parts of the cylinder-piston group and adjusting the valves of the gas distribution mechanism (timing ) and their drives.

Maintenance is carried out at intervals determined by the service book (after the first 300-500 km, and then every 2000 km), or as needed (for example, when operating in dusty conditions or when extraneous sounds, jamming or leaks appear). For the full performance of the work, tools and fixtures are needed, as well as experience working with them.

1. engine systems;
2. tires and drum brakes;
3. battery;
4. free travel of the gas cable;
5. steering column bearings;
6. front disc brake;

The engine oil level should be checked before each ride using the dipstick on the right side of the crankcase. If necessary, add oil of the same grade that was filled into the engine. Simple, but extremely necessary operations - changing the oil and cleaning the filter, they are carried out at each scheduled maintenance.

1. dipstick and oil filler neck;
2. oil filter plug;

To change the oil, warm up the engine, unscrew the filler and drain plugs. When the oil flows out, it is necessary to tighten the drain plug and unscrew the oil filter cap and clean it or, if damaged, replace it with a new one. Then pour the required amount of oil through the funnel into the hole (usually its amount is indicated on the body), controlling the level. After starting the engine for 1-2 minutes, you should check the oil level (it should be at the top mark of the dipstick), and top up if necessary.

The carburetor is adjusted when the idle speed deviates from the norm (the engine "roars" or stalls), or to adjust the composition of the mixture (by changing the position of the metering needle). In this case, it is not necessary to remove the carburetor from the engine; it is enough to separate the luggage compartment and the seat. To clean the carburetor and check (adjust) the fuel level in the float chamber, dismantling the carburetor is required.

Adjusting grooves of the carburetor needle.

Maintenance of the air filter consists in cleaning the filter element and housing. The foam (polyurethane foam) filter element allows repeated cleaning, it is washed in pure gasoline and impregnated with a special oil for air filters. Excess oil must be removed by squeezing the foam rubber (but not twisting it).

After several seasons, it may be necessary to clean carbon deposits from parts of the cylinder-piston group. To carry out these works, you need to remove the cylinder head from the engine and soften the deposits using acetone (wetting a rag with it) or special cleaners. To remove carbon deposits, a scraper made of wood, plastic or thin tin is suitable.

Work on adjusting the valves and the timing drive requires experience and is quite laborious. Of the special devices, a set of probes is required, which must be inserted into the gap between the pusher and the camshaft cam, after turning the crankshaft to its position when both valves are closed (end of the compression stroke). The normal clearance should be 0.08-0.1 mm for intake valves and 0.1-0.12 mm for exhaust valves. Measurements are taken on a cold engine. In addition, it is necessary to periodically adjust the tension of the timing chain drive.

Servicing electric equipment of scooters actually comes down to inspecting, cleaning and timely replacement of the spark plug, and replacing burnt out lamps. At each maintenance, it is necessary to check the condition of the spark plug, and after a run of 4-8 thousand km (depending on operating conditions) or once a year, it is recommended to replace it. A new candle should be installed of the same type, and if it is not there, then another manufacturer, but with the same glow number. During operation, the candle is periodically cleaned of carbon deposits and the gap between the electrodes is adjusted (its value is indicated on the package).

To clean the surface of the battery from traces of electrolyte, it is wiped with a cloth moistened with soda solution, then washed off with water and wiped with a dry cloth. Maintenance of the electric starter is reduced to cleaning the terminals from oxides and tightening the terminal in case of failures.

Transmission maintenance includes: cleaning the internal cavity of the variator housing and changing the oil in the rear wheel gearbox (gear oil is used for this). Periodicity - at the first MOT, and then annually, if not necessary (for example, in case of water ingress). The oil level can often not be checked unless there are signs of oil leakage.The filler hole is aligned with the control one, so you should fill in new oil until its level in the gearbox is equal to the lower edge of the hole.

An important operation is the maintenance of the brakes of the scooter. It includes: cleaning and replacing the pads or brake fluid, adjusting the free play of the rear brake lever, lubricating its cable.

Rear brake lever free play adjustment

Throttle cable free play adjustment

The hydraulic drive hose must not have scuffs and cuts, and there must be no fluid leakage at its joints. To control the fluid level in the reservoir of the main brake cylinder there is a special peephole. Top up, if necessary, the liquid of the exact same type that was previously filled in according to the instructions. It is recommended to change the brake fluid every two years. If the front brake lever "fails", the system must be pumped, removing air.

The condition of the pads can be assessed without disassembling the brake. The minimum thickness of the friction layer is determined visually if the pad has a special wear indicator. It is made in the form of a groove that does not reach the steel base of the pad by the amount of wear limit. If the pad does not have a wear indicator, we measure the thickness of the friction layer - it should not be less than 1-1.5 mm. After replacing the pads, before driving off, it is imperative to press the brake lever several times so that the pads choose excessive gaps (self-adjusting).

Maintenance of a drum brake is reduced to the supply of pads by turning the nut on the threaded end of the cable. With a decrease in the effectiveness of the brakes, which occurs due to contamination (oiling) of the surfaces of the pads and drum, remove the wheel and clean the surfaces with sandpaper or a file, and if necessary, replace the pads. Also lubricate the expander cam axle with engine oil. After cleaning (replacing) the brake pads, the brakes do not immediately acquire normal efficiency, some mileage is required to grind the linings to the drum.

Tire pressure should be checked regularly; it should be 1.8-2.0 atm. This will ensure the safety of travel and maximum service life. The maximum residual tread height of scooter tires (according to the requirements of traffic rules) is 0.8 mm.

In steering, steering column bearings require attention: bearings are not allowed to jam in any position of the steering wheel, as well as their play. Their condition is checked (with the front wheel suspended) by shaking the lower parts of the movable pipes of the fork or the pipe of the linkage with the hands. Adjustment will require two large keys and the removal of the front fascia.

The scooters are fitted with sealed front wheel bearings designed to operate without maintenance for the life of the bearing. For such bearings, care must be taken that the play does not exceed the allowable values ​​(about 2 mm along the rim). If necessary, they should be replaced with new ones.

Article taken

I started a 4 rex scooter from the battery, the speed will drain normally, I take off the terminal from the battery, the speed drops to a minimum, although I give gas to the full, I put the terminal on the battery, the rotation will again drain normally, what is the reason

Most likely, the ignition (rotor-stator) is not working properly, it is also worth checking the operation of the voltage regulator relay

In order for an internal combustion engine to work, it needs three components: fuel, spark, compression. The main slogan of motor mechanics is “miracles do not happen”. It must always be remembered that if, when troubleshooting and scooter repair it turns out that there is a spark, there is compression, fuel comes in, but the engine does not start, this, as a rule, only means that one of these components is actually missing.

Too lazy to give the scooter for repair and pay money for it. Familiar situation.Then it's time to take up repairs with your own hands.

The basic principle of troubleshooting and repairing a scooter is to step by step eliminate the elements of the system, trying to identify the cause of the malfunction in one of them. It is necessary to search and repair strictly sequentially, from the very beginning of the chain to the very end. That is, for example, in the absence of a spark, you should not immediately change the switch. First you need to make sure that the generator is “alive” with us, then test the wiring. Etc.

An important note: if you have a device in front of you, which, according to the owner, “used to work like clockwork”, it makes sense to ask if old gasoline is poured into the tank. A couple of months of storage is enough for gasoline to lose its octane rating to such an extent that it loses its ability to ignite.

It is important to remember that before making a final diagnosis and starting to repair the scooter, you need to make sure that a knowingly working spark plug is installed on it, and the carburetor is also functioning normally.

In addition, you need to know that the correct operation of the engine (even at idle) is closely related to the correct operation of the variator, clutch, as well as the camshaft and valve group. In other words, with normally functioning power, ignition and CPG systems, the problem may be, for example, in the transmission, since the crankshaft torque is directly transmitted to the variator.

When carrying out diagnostics and repairs, it must be remembered that under certain circumstances that led to the need scooter repair, it is necessary to check not a single element, but the entire system. For example, if the carburetor is clogged, provided that the air filter is intact and impregnated, it is necessary to check for dirt in the gas tank and fuel filter. If the scooter has been driving for a long time without an air filter, or with an unimpregnated filter, then everything must be checked: the CPG, the crankshaft and the main bearings.

Below are some of the problems that may occur, as well as the main steps to resolve them. The links indicate the places where you can find information on this item.

In terms of complexity and abundance of systems, this carburetor will compete with the most sophisticated automobile ones (only those with electronic control are more difficult). Hence the advice: if your experience with the motorcycle power system is limited to two or three successful repairs of K-65 devices, do not take risks - contact the specialists. And second: work on a table covered with a sheet of clean white paper under the light of a bright lamp - it's easier to see the details and harder to lose them. And it is extremely difficult to examine the holes of the jets: they are so small that the smallest speck of dust will clog them. Some channels are comparable in size to them. Before disassembly, the carburetor must be clean on the outside. Hands - too, like a surgeon before the operation. To work, you will need screwdrivers with unworn working surfaces. Most of the screws here are not only tightly tightened, but also secured with threadlocker, so that a screwdriver with a bad sting will only break their slots. Stock up on tweezers to make it easier to “catch” the little things. Well, are you scared? If not, let's get started.

You can remove the carburetor through the hatch under the seat, but it will be easier if you first dismantle the entire trunk.

You can get to it through the hatch in the trunk, under the saddle. But it is easier to do this if you unscrew the five bolts and dismantle the entire trunk along with the saddle, loosening the clamps. Loosen the one on the engine side more so that the collar on the rubber pipe can come out of the deep groove on the carburetor outlet pipe. Usually, when the engine is not running, the gas valve with a pneumatic actuator is securely closed, but it is better to play it safe - fix the end of the hose removed from the carburetor above the gas tank. Then disconnect the throttle cable and wire connector A going to the carburetor starter. Clean the carburetor with a soft brush from dust, wash your hands and start disassembling.

Remove the three bolts and remove the float chamber cover. The axis of the floats holds the bolt. Unscrew it and take out the block of floats with a locking needle. The needle of this carburetor has a rubber conical part, and a spring-loaded rod rests against the float tongue. This design makes the unit hermetic, very durable and resistant to abrasive wear.

Back view : 1 - starting device; 2 - channel leading to the cavity under the spool membrane; 3 - air channel of the starting device; 4 - air jet of the main dosing system; 5 - accelerator pump atomizer; 6 - the channel in which the air jet of the idle system is located; 7 - accelerating pump.

Possible malfunctions. The tide on the side walls of the floats should be parallel to the plane of the upper carburetor connector. If this is not the case, bend the metal tab to achieve the correct position. Check it with the carburetor on its side - the tongue should only touch the needle shaft, but not sink it.

Front view : 1 - channel for the exit of the air-fuel mixture from the starting device; 2 - a tube through which excess gasoline is drained in case of a malfunction of the float mechanism; 3 - a channel through which the vacuum from the intake manifold is supplied to the idle system shutdown mechanism.

Main dosing system

Its jet is located in the center of the float chamber. Through it, the fuel enters the emulsion tube, where it mixes with air and forms an emulsion. Air enters through a jet located at the carburetor inlet. The emulsion is dosed by a needle, which is fixed in the spool. A constant vacuum in the atomizer zone is provided by the spool. There is a hole next to the dosing needle through which the vacuum is transferred to the cavity above the membrane, while the spring is compressed, and the spool rises to the desired height.

Right side view : 1 – accelerator pump drive lever; 2 - throttle actuator sector; 3 - screw for adjusting the amount of air-fuel mixture at idle.

To lean or enrich the combustible mixture, unscrew the screws securing the membrane cover and remove the spool with the membrane. Be very careful - the cover is made of fragile plastic. Remove the needle plug and the needle itself from it.

The adjustment range is small - there are only three grooves on the needle, with factory adjustment, the stopper is in the middle. During engine operation, due to air vibrations in the intake tract, vibrations of the spool occur. To prevent the stopper from breaking the groove of the needle, a rubber ring is installed under it. If you damage or lose it, then not only shorten the life of the assembly, but also lean the mixture - the needle without this part will drop lower.

Left side view : 1 - quality adjustment screw at idle; 2 - fuel inlet fitting; 3 - fitting through which you can sleep fuel from the float chamber; 4 - screw-plug of the float chamber.

When you install the membrane in place, make sure that the protrusion on it falls into the depression on the body.

Possible malfunctions. There may be two. The first is a clogged fuel jet. Blow it out. The second - the spool membrane was damaged. In this case, it is impossible to do without replacing the membrane with the spool.

Parts in the float chamber : 1 - fuel tube of the starting device; 2 - block of floats; 3 - locking bolt; 4 - a needle with a rubber tip and a spring-loaded rod; 5 - axis; 6 - tongue; 7 - main fuel jet. eight - . and its emulsion tube; 9 - idle fuel jet.

Idling (XX), as in most carburetors, is regulated by two screws: the quality and quantity of the mixture. The quality screw is located under the throttle valve axis on the left side of the carburetor, and the quantity screw is located on the axle sector stop. At the factory, the quality adjustment is carried out as follows: the screw is tightened to the stop, and then unscrewed by 2.5 turns.The XX system fuel jet is located next to the main fuel jet and is integral with the emulsion tube. The air jet is pressed into a tube-like boss to the right of the air jet of the main fuel system. The emulsion is supplied to three holes under the throttle valve. Why three? As the damper opens, its slice moves from one to another, and they alternately find themselves in the zone of the highest air flow velocity, and therefore, in the zone of the greatest rarefaction. This improves the performance of the carburetor at the beginning of the throttle opening and eliminates “dips”.

When installing the spool, make sure that the protrusion on the membrane must be in the cavity of the body (highlighted in red). The arrow indicates the hole through which additional air enters the idle system to turn it off.

With a sharp opening of the throttle, the vacuum near the atomizer decreases, it is not enough to suck in a sufficient amount of gasoline - and a “failure” occurs in the engine. The purpose of the accelerator pump, as its name implies, is to help the engine accelerate the scooter during this "confusion" of the carburetor.

The carburetor on a scooter is an important part of the engine power system and is responsible for supplying fuel to the engine cylinders. But due to wear and tear, your carburetor may need to be repaired over time.

In this article, we will tell you how to repair the carburetor of a scooter with a 2-stroke and 4-stroke engine with a volume of 50 and 150 cubic meters, and also explain how to install and adjust a new carburetor on a scooter
The content of the article:

• Removing and cleaning the carburetor
• carburettor installation,
• Adjustment (setting) of the carburetor,
• repair video,
• Our production,

In order to remove the carburetor from the scooter, the first step is to remove all the plastic that prevents access to the carburetor (usually you have to remove the seat and the plastic under the seat). Then we disconnect the fuel and oil hoses (there are oil hoses only on a 2-stroke scooter), the contacts of the starting enricher. After that, unscrew the bolts securing the carburetor to the engine.

Now, after the carburetor has been removed, it is necessary to clean its outer surface from dirt and dust. Can be washed in gasoline and wiped with a dry cloth.

The next step is to partially disassemble the carburetor, namely: unscrew the bolts securing the float chamber cover (2 bolts), then carefully remove the float so as not to bend the plate. We wash the cover of the float chamber very carefully from the inside. Now you can start cleaning the inside of the scooter carburetor itself.

2 easy ways to clean your carburetor:

1) Rinse in gasoline, then purge with a compressor with a nozzle in the form of a pointed tip (this will effectively purge all channels).

2) We buy a can of liquid for cleaning the carburetor. Thoroughly clean all channels and carburetor jets. The spray can also replace the compressor, since the liquid from it is supplied under high pressure, which allows you to effectively clean small channels.

When cleaning, special attention must be paid to all channels and jets (we unscrew the jets during cleaning). We also remove the starting enricher and clean its channels. It is not necessary to dry the internal parts of the carburetor. Now we can put on the float and assemble the carburetor in reverse order.

We install the carburetor on the scooter in the following sequence:

• 1) We fix the carburetor in the place of attachment with the engine, put on the air pipe and fix it with a clamp.
• 2) We put the drain hose on the fitting (lower part of the float chamber)
• 3) We install the gas cable in a special bracket.We check that the protrusion on the cable fastening screw coincides with the groove on the bracket. We fix the cable with nuts
• 4) We put on the gasoline hose and fix it with a spring clamp.
• 5) Connect the contacts of the starting enricher.

As you can see, the connection diagram of the carburetor on the scooter is not so complicated. Next, you need to adjust the carburetor.

Carburetor adjustment on a scooter consists of several stages, which include: idle speed adjustment, mixture quality adjustment and float chamber fuel level adjustment.

Setting the carburetor 2t and 4t scooter has no fundamental differences, except that on some carburetor models there may be no screw for adjusting the quality of the mixture and therefore the quality of the mixture has to be adjusted only by adjusting the needle and float in the carburetor of the scooter

It is necessary to carry out idle speed adjustment on the scooter engine warmed up for 12-15 minutes. Adjustment is carried out using the idle screw, which is installed on each scooter and which allows you to achieve stable engine idling. Turning the screw clockwise will increase the speed, while loosening it will decrease it. We warm up the scooter and achieve stable idling by adjusting the screw.

2-stroke scooter carburetor (Honda Dio)

4-stroke scooter carburetor

1 - idle screw, 2 - mixture quality screw

1 - mixture quality screw, 2 - fuel inlet fitting, 3 - fitting for draining fuel from the float chamber, 4 - screw plug of the float chamber.

The quality of the mixture is very important when adjusting the carburetor, because a lean mixture can overheat the engine and lose power, while a rich mixture forms carbon deposits in the combustion chamber.

The quality of the mixture is adjusted using the adjusting screw. The mixture becomes richer when we turn the screw clockwise and leaner when we turn it counterclockwise.

The adjustment scheme looks like this:

• We warm up the scooter for 10 minutes, turn off the engine,
• Tighten the screw to the end clockwise,
• Unscrew 1.5 turns counterclockwise
• We start the engine and turn the screw back another 1/3 turn. Let the engine run for 2 minutes.
• If the speed increases, then unscrew the screw another 1/4 turn counterclockwise. Also let the engine run for 2 minutes.
• Repeat the previous step until the RPM starts to drop (don't forget to let the engine run for 2 minutes before each change)
• If the speed began to fall, then screw the screw clockwise by 1/4 turn.

Thus, stable operation of the engine at any permissible speed is achieved. Ideally, the engine should work well in the position of the mixture quality adjustment screw unscrewed by 1.5 - 2 turns. However, due to wear of engine parts, this range may vary. If the carburetor of your scooter does not have a screw for adjusting the quality of the mixture, then the adjustment must be carried out only by adjusting the position of the carburetor needle. Raise the needle - the mixture is enriched, lower the needle - the mixture is leaner.

By soot on the candle, you can find out about the incorrect adjustment of the quality of the mixture. If the soot on the candle is black and there is a lot of it, the mixture is too rich. If the soot is almost white, the mixture is too white.

The fuel level in the float chamber can be checked using a transparent tube at the bottom of the carburetor. In order for this to be done, it is necessary to unscrew the cream screw, lift the tube towards the top of the carburetor. Now we check the fuel level with the scooter running. It should be just below the protruding skirt where the float chamber cover attaches to the carburetor.

If the level is low or, as it happens more often, too high, then it is necessary to remove the cover and adjust the moment of operation of the locking game by bending the needle holder (small antennae) in a very small range.

It is worth remembering that, if the carburetor malfunctions or its internal elements are dirty, adjusting the carburetor may only temporarily solve the problem.

That's the whole principle of setting up a carburetor on a Chinese and Japanese (Honda, Suzuki, Yamaha, etc.) scooter. Now you can independently repair and adjust the carburetor on a 2t and 4t scooter engine with a volume of 50 and 150 cubic meters.