DIY 4-stroke scooter engine repair

In order for the engine of a four-stroke scooter to work perfectly, only three things are needed: spark, fuel and compression. When troubleshooting, you should adhere to the following rule - everything is checked gradually, from the most elementary malfunctions to 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 we check for a spark. The engine will not start if the quality of the mixture is disturbed, or if the carburetor is clogged.

If the ignition key is not turned, a fuse is blown, or the battery is discharged, the engine will show no signs of life. Therefore, before proceeding with a global repair, you should check these reasons.

The starter motor cranks, but the engine will not start.

Possible reasons - the spark plug is broken, the carburetor is clogged, the fuel does not enter the system.

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

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 could be a sign that the bearings are out of order and need to be replaced. It may also be associated with 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. Disconnect all wires from the engine and the throttle cable from the carburetor. Remove the gas hose and vacuum filter. Disconnect the rear shock absorber. After the engine has been separated from the frame, unscrew the nut on the mounting axle and remove the axle. After removing the engine, it is advisable to wash it.
2. Removing the cylinder head. It is necessary to do to clean the chamber from carbon deposits. 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 body. We unscrew the bolts on which the cylinder is attached and remove the chain, and then the cylinder head itself.
3. Valve clearances must be adjusted 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 is related to the mark on the engine housing. We measure the clearance between the adjusting screw and the valve stem. When increasing or decreasing the gap, we adjust by rotating the screw.

As practice shows, it is better to entrust the engine overhaul to professionals, since there are many nuances that an ordinary driver does not pay attention to, but which in the future can create even greater problems and then more expensive repairs will be required.
A video on 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 up, the brake lever limit switch does not work.
Analytics: the lever of one of the brakes has not been pressed or there is a malfunction in the brake light circuit.
Procedure: replace the bulb, adjust the brake lever free play or replace the brake lever limit switch.

Crime: fuse blown.
Procedure: check and, if necessary, replace the fuse for the main circuit and the starter circuit.

Crime: the junction of the terminal with the wire is covered with a loose coating of oxides.
Analytics: the battery gives insufficient voltage, which can happen due to a malfunction 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: the electric starter circuit is faulty.
Actions: clean the contacts on the relay and starter, "ring" 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 stroke of the kick-starter lever.
Analytics: Kick starter or ratchet gear teeth are broken. 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 - see). Variants of reasons: the filter of the gas valve is clogged, the gas valve is faulty, the fuel line is clogged, the vacuum hose for the control of the gas valve has jumped off or is leaking.
Actions: clean the fuel tap filter, blow through the fuel line, make sure that the automatic gas tap is in good working order.

Crime: fuel is supplied to the carburetor, but does not enter the pop-up chamber.
Analytics: float fuel valve stuck.
Procedure: remove the float chamber cover and clean the valve seat. If it does not help, replace the valve.

Crime: you unscrew the candle, and it is "wet" - covered with a layer of unburned benzo mixture.
Analytics: excessively rich combustible mixture, which happens due to too high fuel level in the float chamber or due to clogged air filter.
Actions: disassemble the carburetor, check the fuel level, clean the air filter.
Side effects: The engine starts immediately if a little gasoline is poured into the air filter.
Analytics: the automatic starting enrichment does not work.
Actions: check the serviceability of the starting enrichment (there are several ways - they are described in detail in the repair manuals)

Crime: a spark does not occur on a spark plug unscrewed from its socket (in a position where the metal part of the spark plug reliably contacts the "mass" of the scooter).
Analytics: the spark plug is faulty: the insulator is broken or the electrodes are covered with a thick layer of carbon.
Procedure: Clean the spark plug with emery paper or replace. If the spark still does not appear, diagnose other elements of the ignition system.

Crime: the spark on the spark plug is formed, but weak or "running".
Analytics: the insulator is broken at the spark plug.
Action: replace the spark plug.

2. THE ENGINE STARTS WITH LABOR, RUNNING UNSTABLE
Crime: the engine does not "spin", there are pops in the carburetor.
Analytics: excessively lean fuel mixture, a possible cause - air is sucked in through a loose intake manifold or damaged crankshaft oil seals. Water in the float chamber.
Procedure: replace the gasket under the branch pipe and evenly tighten the bolts of its fastening. Replace the crankshaft oil seals. Get rid of the water in the float chamber (by unscrewing the drain screw of the float chamber), blow out the jets and channels of the carburetor, replace the gasoline in the tank.

Crime: a spark on an unscrewed spark plug (in a position where its metal part reliably contacts the "mass" of the scooter) is formed, but the surfaces of the insulator and electrodes are dry.
Analytics: the automatic starting enrichment does not work (if the engine is cold). Normal combustible mixture does not form. The idle air jet is clogged.
Actions: check the serviceability of the starting concentrator (see item 1). Purge the carburetor jet and channels.

Crime: there are water droplets on the insulator and electrodes of a twisted spark plug. Analytics: water penetrated into gasoline.
Action: get rid of water in the float chamber.

Crime: a spark on an unscrewed spark plug (in a position where its metal part reliably contacts the "mass" of the scooter) is formed, but the surfaces of the insulator and electrodes are covered with black oily soot (photo 5).
Analytics: the brand of the spark plug does not correspond to the thermal mode of the engine operation - its glow rate is higher than that set for the given engine (the spark plug is "cold"). The temperature in the working area of ​​the plug 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 work 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 to the atmosphere are clogged.
Procedure: Clean the fuel tank cap vent or hoses.

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

Crime: the sound of escaping gases is heard, oily traces are formed on the head and cylinder.
Analytics: the gasket under the cylinder head is damaged or the fastening of the head to the cylinder is loose.
Actions: replace the gasket and tighten the nuts securing the head to the cylinder with the required torque (effort) in the sequence recommended by the repair manual.

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

4. ENGINE STOPS AT SHARP OPENING OF THE THROTTLE
Circumstance 1: The engine has just started.
Analytics: the engine is not warm enough.
Action: continue warming up the engine at idle speed.

Circumstance 2: The engine is well warmed up.
Analytics version 1: carburetor not adjusted.
Actions: adjust idling speed, if necessary - the main dosing system (see item 5).
Version 2: the variator does not work properly.
Actions: see item 10.

5. THE ENGINE STARTS NORMALLY BUT IT DOESN'T SPIN
Crime: thick smoke in the exhaust, excessive fuel consumption, black plaque on the spark plug electrodes.
Analytics: The main dosing system prepares an overly rich mixture.
Actions: adjust the quality of the mixture - lower the carburetor throttle adjusting needle one notch (groove) down. It may be necessary to install a smaller bore main jet.

Crime: the engine overheats, detonation is heard during acceleration, white bloom on the electrodes and spark plug insulator. After turning off the ignition, the engine continues to run for a few seconds (detonates).
Analytics: The carburetor's main metering system is preparing an overly lean mixture.
Actions: adjust the quality of the mixture - raise the carburetor throttle adjusting needle one step up.It may be necessary to install a large bore main fuel jet.

Crime: the engine runs unusually quietly (although it is easy to start), low-smoke exhaust, the engine “does not pull” during acceleration.
Analytics: muffler, channels and cylinder windows clogged with carbon deposits (in two-stroke engines).
Action: clean carbon deposits if possible. If the muffler is completely clogged (no air flow), replace the muffler.

6. AFTER A LONG DRIVE, THE ENGINE LOSES POWER
Circumstance 1: an air-cooled engine.

Crime: no air movement is felt from under the cylinder casing, and a sheet of paper does not "stick" to the air intake mesh (on the right side of the engine) (if a test is carried out with paper).
Analytics: the fan impeller blades are broken, another assumption is that the shrouds of the cooling system are loose or split in places.
Procedure: Replace the impeller and damaged covers.

Circumstance 2: Liquid-cooled engine.
Crime: coolant leaks, its level in the tank has dropped.
Analytics: faulty components of the system: pump, thermostat, radiator.
Action: replace faulty components.

7. ENGINE DOES NOT ACCELERATE THE SCOOTER TO 50 KM / H
Inspection data: speedometer calibrated, no power or rev limiter installed.
Analytics version 1: The scooter is not designed for this 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.
Actions: see item 2 or change the scooter.
Version 3: the variator is not working properly.
Actions: see p. 9, 10.

8. WHILE THE ENGINE IS RUNNING THE SCOOTER DOES NOT START FROM THE PLACE.
Crime: the variator is faulty.
Analytics: the driven pulley spring is broken, the V-belt is torn (to make sure of this, remove the variator cover - breakdowns are perceived at a visual level).
Action: replace defective parts.

Crime: faulty centrifugal clutch.
Analytics: the springs of the shoes are broken, the linings of the shoes are excessively worn out (found out during a visual inspection after removing the variator cover) (photo 9). Action: replace defective parts.

9. SCOOTER RIDES IN SPECTS
Crime: jerks are felt when driving.
Analytics: the variator belt slips (due to wear, damage or oiling) or the surfaces of the pulleys are excessively worn out.
Action: replace defective parts (photo 10).

10. SCOOTER SPEEDS SLOWLY, RIDES SLOWLY
Analytics: during the recent tuning, the weight of the centrifugal regulator weights or the spring of the driven pulley are incorrectly matched. The springs of the centrifugal clutch shoes are broken or have lost their rigidity, the linings of the centrifugal clutch shoes are worn or oiled.
Actions: carry out the tuning more thoroughly, preferably with the participation of specialists.

In order to disassemble the engine of a Chinese scooter, you do not need to be a super-mechanic or an overly gifted person. First of all, you need desire, accuracy and the availability of the necessary tool. Unfortunately, there is nowhere without a good tool. There are, of course, people who repair scooters with a crowbar and a sledgehammer, but if you do it for yourself and for a long time, then you need to use only good tools. If you do not have the tools, then it is better to leave this venture.

• Alternator puller (you can do it yourself)
• CVT puller (you can do it yourself)
• Kickstarter sprocket remover (157QMJ engine only)
• Heads for 8, 10, 12, 17 mm
• Phillips and flat head screwdriver
• Small hammer
• Wish

Most of China's four-stroke scooter engines can be classified into two main types

1. First type: 139QMB-series engine. This engine is very popular in the CIS countries and is installed on most Chinese four-stroke scooters.
2. Second type: 157QMJ-series engine.This engine has a larger volume than the first one and, due to the higher price, is not so popular.

Basically, these two engines are a copy of the ancient Honda GY6 and differ from each other in displacement, kickstarter design, oil pump drive and electric starter drive. Otherwise, these engines are identical.

Typical 139QMB, in fact JL1P139QMB-2

And this is how a typical 157QMJ looks like, in fact LK162QMK

We remove the engine from the frame, drain the oil, clean off the manure of the year before last from all visible surfaces, blow out all the cracks and cavities with a compressor, put it on the cutting table and proceed to an extremely interesting and exciting activity ...

• Remove the muffler
• Remove the cooling shrouds
• Remove generator
• Remove variator
• Clean and blow off connectors
  

It is very easy and simple to remove the muffler: we unscrew two nuts and two bolts on the cylinder head that secure the muffler to the frame (139QMB) or the rear wheel amplifier (157 QMJ)

The cooling shrouds are even easier to remove: we turn off all the bolts and self-tapping screws that attach the shrouds to the engine and remove.

But the generator is not so simple. The generator can only be removed with a puller. All your attempts to knock down the rotor with a hammer or pick it up with a crowbar are doomed to failure in advance.

We unscrew the bolts on the cooling impeller and remove it and the rotor

We fix the rotor with a puller and unscrew the nut (right thread)

We install the puller and pull the rotor off the crankshaft journal

We blow out the generator, unscrew the bolts and remove it somewhere further

Remove the variator cover. There is nothing difficult in this: we turn off all the visible bolts and remove the cover from the engine. On the 157QMJ engine, so as not to bend the kickstarter return spring bracket, first remove the crank, remove the retaining ring from the kickstarter shaft, and only then remove the cover itself. You can, in principle, and so remove, but then you have to trim the bracket a little.

Removing the variator is not much easier than removing the generator. As with a generator, you need a good puller. Fortunately, the puller can be made by yourself: for the 139QMB engine, instead of the puller, you can use a metal plate: remove the bendix from the niche, insert the plate into it, rest the variator impeller tooth against the plate and unscrew the nut.

You can also make a more advanced puller: we are looking for an unnecessary clutch disc from an IZH motorcycle, we weld a bar and several hooks for the impeller teeth to it

For the 157QMJ engine, the puller is done a little differently.

You can go to the nearest tool store and buy a universal wrench for the grinder. For removing the variator of the 157QMJ engine, it fits very well and costs a penny

The principle of removing the variator is identical to that of removing the generator: fix the impeller with a puller, unscrew the nut, remove the variator from the axle. After removal, we completely disassemble the variator and check all its parts for wear.

On the 157QMJ engine, there is a kickstarter gear behind the variator. It is not so easy to remove, but if you are going to subsequently half the engine, you will have to remove it.

We clean and blow out the cylinder connectors, cylinder head and valve covers. We unscrew the bolts on the valve cover and remove it from the head

We turn off the nuts and bolts on the cylinder head

Remove the camshaft bed. The camshaft bed is virtually wear-free. After removing it, it is enough to wash it and check for cracks

We remove the chain from the camshaft and take it out of bed. The camshaft has two problem points that are worth paying attention to: wear of the thrust bearings and cam sliding surfaces

The cylinder, head and camshaft bed are centered relative to each other using guide bushings. These bushings have the ability to fall out of the sockets and then try to find it. To avoid this - immediately remove the bushings and put them somewhere further away.Hereinafter, the bushings will be indicated by arrows.

Remove the cylinder head. The cylinder head is the most vulnerable part of the engine and the operating parameters of the engine directly depend on its condition. In order not to have problems later: the head must be completely disassembled, inspected for cracks, cut the valve seats, put new valves, grind the valves to the seats, put new oil seals and grind the plane on the plate or milled

Remove the cylinder. We check the cylinder immediately after removal for liner wear and the presence of seizures on the mirror

We take out the retaining ring from the piston boss, push the finger out of the upper connecting rod head, remove the piston. We check the piston for cracks and wear, pay special attention to the condition of the grooves for the rings and the rings themselves

We unscrew the bolts on the cover (there are less bolts by 139QMB: 8), slightly hammer it with a mallet and remove it from the engine. The crankcase guides will be marked with arrows as in the case of the cylinder head. The covers, especially on 139QMB engines, break even if the scooter falls slightly. When you remove the cover - carefully inspect its body and if the cracks are not significant - weld them at the nearest "argon"

157 QMJ looks more complicated inside

To disassemble 157QMJ you need to do the following:

• Remove the starter intermediate gear
• Unscrew the nut on the freewheel
• Remove the chain from the oil pump
• Unscrew the last bolt tightening the engine crankcase

With 139QMB, much less fuss:

• Remove the oil pump gear
• Unscrew the last bolt tightening the crankcase

We take an old blunt screwdriver and use a hammer to unscrew the freewheel nut (left-hand thread: unscrew strictly clockwise!)

Press on the drive chain:

• A good chain should have some slack. Such a chain can still be operated
• If the chain is worn out, the slack will be maximum. Such a chain should be thrown out.

The chain is in average condition. The new chain practically does not sag when pressed on it

Remove the protective screen of the oil pump

We put a tin bar or stick under the chain, unscrew the nut on the oil pump sprocket, remove the sprocket from the shaft, remove the chain

On 139QMB we do almost the same thing: hold the sprocket with our hand, unscrew the nut, remove the gear from the shaft. On some 139QMB models, the gear can be without a nut, if you have done so, then you are in luck: take out the gear and housings and that's it.

We unscrew the last bolt tightening the crankcase and use a wooden mallet to half the engine

We take out the crankshaft from the crankcase and check it for suitability for further operation

We check the timing chain for wear, but it will be better if you throw it away immediately. At this, the epic with the disassembly of the engine can be considered over. As you can see, there is nothing difficult in this. But it is up to you to disassemble the engine yourself or send it to the workshop.

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• Repair of 4 stroke scooter engine

Anything can break. Even the most reliable and easy-to-use scooter engine. Untimely maintenance and repairs, poor fuel, minor failures left unattended, all can cause serious engine malfunctions.

Loaders, as a whole, and anyone.

There are many articles on the Internet.

Older car models have engines.

Renault in Russia Renault belongs to.

The Skoda Octavia station wagon gets great reviews.

The car generator is an indispensable element during.

The most expensive part of a vehicle is.

Modern technical means make it possible to maintain favorable.

Carried away by the selection of engine oil for your own.

Let's get down to the basics of technical inspection

Although four-stroke scooters are more resourceful than two-stroke scooters, they, like any equipment, need timely maintenance (MOT) 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 at the request of the owner, he can carry out all the work on his own. The main work on the maintenance of 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 drive.

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 execution of work, tools and devices are needed, as well as experience in working with them.

1. engine systems;
2. tires and drum brakes;
3. storage battery;
4. free running of the throttle 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, the oil should be topped up with the same grade that was added to the engine. Simple, but extremely necessary operations - oil change and filter cleaning, they are carried out at every 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, screw the drain plug and unscrew the oil filter cover and clean it or, if damaged, replace it with a new one. Then pour the required amount of oil through a funnel into the hole (usually its amount is indicated on the body), controlling the level. After starting the engine for 1-2 minutes, check the oil level (it should be at the upper 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 sufficient to separate the luggage compartment and the seat. Removing the carburetor is required to clean the carburetor and check (adjust) the fuel level in the float chamber.

Adjusting grooves on the carburetor needle.

Air filter maintenance consists of cleaning the filter element and housing. The foam (polyurethane foam) filter element allows multiple 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 up 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 (moistened with a rag) or special cleaners. A scraper made of wood, plastic or thin sheet metal is suitable for removing carbon deposits.

The 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, having previously turned the crankshaft to such a 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 carried out on a cold engine.In addition, it is necessary to periodically adjust the tension of the timing chain.

Maintenance of scooter electrical equipment actually comes down to inspection, cleaning and timely replacement of the spark plug, and replacement of 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 terminals in case of malfunctions.

Maintenance of the transmission includes: cleaning the inside of the casing of the variator and changing the oil in the rear wheel gearbox (for this, transmission oil is used). Frequency - during the first maintenance, and then annually, if not necessary (for example, when water gets in). The oil level can often not be checked unless there are signs of oil leakage. The filler hole is aligned with the control hole, so new oil should be added until its level in the gearbox is equal to the lower edge of the hole.

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

Rear brake lever free play adjustment

Adjusting the free play of the throttle cable

The hydraulic hose must be free of scuffs and cuts, and there must be no fluid leakage at its joints. There is a special peephole to control the fluid level in the reservoir of the master brake cylinder. Topping up, if necessary, should be liquid of exactly the same type that was poured earlier according to the instructions in the instructions. It is recommended to replace the brake fluid every two years. If the front brake lever fails, the system must be pumped to remove 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 shoe by the amount of wear limit. If the pad does not have a wear indicator, measure the thickness of the friction layer - it should not be less than 1-1.5 mm. After replacing the pads, before leaving, be sure to press the brake lever several times so that the pads select excessive clearances (self-align).

Servicing a drum brake is reduced to the supply of shoes by rotating the nut on the threaded cable end. If the efficiency of the brakes decreases, which occurs due to contamination (oiling) of the surfaces of the pads and the drum, you should remove the wheel and clean the surfaces with sandpaper or a file, and, if necessary, replace the pads. The axle of the expander cam is also lubricated with engine oil. After cleaning (replacing) the pads, the brakes do not immediately acquire normal efficiency; some mileage is required to grind the pads to the drum.

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

In steering, the steering column bearings require attention: seizing of bearings in any position of the steering wheel, as well as their backlash, is not allowed. Their condition is checked (with the front wheel suspended) by swinging the lower parts of the movable tubes of the fork or the tube of the link suspension with your hands.The adjustment requires two large keys and the removal of the front trim panel.

The scooters are equipped with sealed front wheel bearings, designed to operate without maintenance throughout the entire bearing life. In such bearings, it is necessary to ensure that the backlash does not exceed the permissible values ​​(about 2 mm around the rim). If necessary, they should be replaced with new ones.

Article taken

I started 4 such a scooter from the accumulator, the revolutions will blow out normally, I throw off the clem from the accumulator, the speed drops to a minimum, although I give the gas to the full, I put the clem on the accumulator, the turnover will blow out normally what is the reason

Most likely, the ignition (rotor stator) is not working properly, it is also worth checking the performance 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 the motorcycle mechanic is “there are no miracles”. 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 usually means only that some of these components are actually missing.

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

The basic principle of troubleshooting and repairing a scooter is to exclude system elements step by step, trying to identify the cause of a malfunction in one of them. Search and repair must be carried out 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 we have a "live" generator, 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 a clock”, it makes sense to ask if old gasoline is poured into the tank. A couple or three months of storage is quite enough for gasoline to lose its octane number to such an extent that it has lost the ability to ignite.

It is important to remember that before making the final diagnosis and starting the repair of the scooter, you need to make sure that a working candle is installed on it, as well as the carburetor is functioning normally.

In addition, you need to know that the correct operation of the engine (even at idle) is closely tied to the correct operation of the variator, clutch, as well as the camshaft and valve group. In other words, with normally functioning power supply, 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 some 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 if there is any 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 untreated filter, then everything must be checked: the CPG, the crankshaft and the main bearings.

Below are some of the problems that you may encounter and the basic steps to take to fix them. The links indicate the places where you can find information on this item.

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

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;
• Installing the carburetor;
• Adjustment (tuning) of the carburetor;
• Repair video;
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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, we 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 off 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 float chamber cover itself 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) We wash it in gasoline, then we purge using a compressor with a nozzle in the form of a pointed tip (this will effectively purge all channels).

2) We buy a can with a liquid for cleaning the carburetor. Thoroughly clean all channels and nozzles of the carburetor. Balonchik also replaces the compressor, since the liquid is supplied from it under high pressure, which makes it possible to effectively clean the small channels.

When cleaning, special attention must be paid to all channels and jets (unscrew the jets during cleaning). We also remove the starting concentrator and clean its channels. It is not necessary to dry the inside of the carburetor. Now we can put on the float and assemble the carburetor in the 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 secure it with a clamp.
• 2) We put on the drain hose on the fitting (the lower part of the float chamber)
• 3) Install the throttle 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 secure it with a spring clamp.
• 5) Connect the contacts of the starting enrichment.

As you can see, the connection diagram for the carburetor on a scooter is not that complicated. Next, you need to adjust the carburetor.

Adjusting the carburetor on a scooter consists of several steps, which include: adjusting the idle speed, adjusting the mixture quality and adjusting the fuel level in the float chamber.

The carburetor setting of a 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 adjust the idle speed on the scooter engine warmed up for 12-15 minutes. The adjustment is carried out using an idle screw, which is installed on each scooter and which allows the engine to run at idle speed stable. When the screw is tightened clockwise, the revolutions increase, when unscrewed, it decreases. We warm up the scooter and achieve stable engine idling by adjusting the screw.

5 - idle screw on a 4-stroke scooter

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

We adjust the quality of the mixture using the adjusting screw. The mixture is enriched if we turn the screw clockwise and depleted when we turn it counterclockwise.

The adjustment scheme looks like this:

• We warm up the scooter for 10 minutes, turn off the engine;
• We tighten the screw clockwise to the end;
• Unscrew 1.5 turns back counterclockwise
• We start the engine and turn the propeller back another 1/3 turn. Let the engine run for 2 minutes.
• If the revolutions increase, then unscrew the screw another 1/4 turn counterclockwise. We also let the engine run for 2 minutes.
• We repeat the previous step until the rpm starts to drop (do not forget to let the engine run for 2 minutes before each change)
• If the revolutions began to fall, then turn the screw clockwise by 1/4 turn.

Thus, stable operation of the engine is achieved at any permissible speed. In the ideal case, the engine should work well in the unscrewed position of the screw for adjusting the mixture quality by 1.5 - 2 turns. However, due to wear of engine parts, this range may change.

If the carburetor of your scooter does not have a screw for adjusting the quality of the mixture, then the adjustment should 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 the soot on the candle, you can find out about the incorrect adjustment of the quality of the mixture. If the carbon deposits on the candle are black and there is a lot of it, the mixture is too rich. If the carbon is almost white, the mixture is too white.

The fuel level in the float chamber can be checked with a transparent tube on the bottom of the carburetor. In order for this to be possible, 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 engine running. It should be located just below the protruding skirt where the float chamber cover is attached to the carburetor.

If the level is low or, as is often the case, too high, then it is necessary to remove the cover and adjust the moment of triggering of the locking game by bending the needle holder (small tendril) 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 tuning the 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.