Snowmobile Buran carburettor tuning. Mikuni carburetor adjustment on a taiga snowmobile

Snowmobiles "Buran" are equipped with several types of carburetors. One of the most popular fuel devices is the Mikuni Buran carburetor. It is an economical trouble-free mechanism. Due to its simple design, easy maintenance, it has won a lot of fans all over the world. All owner reviews of this type of carburetor are invariably positive.

Types of carburetors

The operation of technical facilities in the winter period requires a special approach to the quality of the main components and mechanisms. The preparation of the fuel mixture is carried out at constant sub-zero temperatures. Therefore, in the Buran snowmobile, the manufacturer practices the installation of a Mikuni carburetor on the Buran snowmobile.

Mikuni carburetor on Buran

As an analogue for Russian snowmobile enthusiasts, the manufacturer often uses the installation of Chinese carburetors with the same name. Since the carburetor components are exactly the same, it is necessary to choose a carburetor carefully so as not to confuse their manufacturers. For complete certainty, it is necessary to require supporting documents and certificates from the manufacturer's country from the seller.

Mikuni carburetor device on a snowstorm

The Mikuni carburetor is a single-chamber mechanism with a central float chamber. The design of this assembly uses a cylindrical vertical stroke choke. There is no need to use complex tools and expensive fixtures to mount the carburetor.

This carburetor is good because it is attached directly to the engine nozzle with two M6 bolts. It is not necessary to adjust the gaps, the fastening is rigid, classic, through two rectangular gaskets made of petrol-resistant rubber. The cross section of the gasket material is 1 mm; the gaskets are glued onto rectangular pipes in special grooves for attaching to the engine.

A diffuser and a rubber adapter are installed between the engine and the carburetor. Fuel is taken from the sump filter and the fuel pump through an elastic rubber hose with a cross section of 10 mm to the carburetor intake fitting. Next to it, a 3 mm pump hose is connected with a thin transparent PVC tube.

From the control handles of the snowmobile "Buran" two cables are stretched. One cable controls the fuel supply, it is called gas, the second cable controls the enricher - the air damper. Both cables are equipped with bosses that are easily inserted into the working attachment and control units.

Overall and connecting dimensions of the Mikuni carburetor:

• the distance between the M6 ​​bolts for mounting the carburetor - 48 mm;
• diameter of the passage hole for the fuel mixture entering the combustion chamber - 26 mm;
• the total height of the case is 138 mm.

The design of the mechanism uses a simple round-throttle damper. This node is made in the form of a full-fledged suction, which has two positions:

⇓ First position – flag is down. The fuel channel is closed in this position.

⇑ Second position - the flag is raised. The fuel channel is open in this position.

The principle of operation of the air damper

With two choke positions, the Buran's Mikuni carburetor is the most dynamic and responsive fuel delivery mechanism of any snowmobile in its class. This choke is truly unique among most snowmobiles operating in harsh winter conditions, in severe frost.

The presence of two full-fledged working positions allows you to qualitatively regulate the amount and volume of the enriched fuel mixture entering the ignition chamber of the internal combustion engine. Below (Fig. 2) is an analysis of each of the positions of the air damper.

In the standard position, when the lever is lowered, the additional channel for the enriched fuel mixture is closed. The snowmobile engine receives only the amount of fuel that is directly supplied by the carburetor.

Open channel position. The flag is raised, the additional channel for supplying the fuel mixture is open. Additional fuel enters the combustion chamber of the engine, the power unit develops maximum power.

The role of the flag in the carburetor

It is not in vain that the carburetor on Buran is equipped with a special flag that serves to open an additional channel. This unit plays a crucial role in power characteristics, starting a cold engine in winter, and the speed of warming up the engine on a snowmobile to working condition.

Rice. 2. The main elements of the Mikuni carburetor: 1 - a flag, 2 - a fuel intake fitting, 3 - an adjustment screw, 4 - a pumping fitting.

If you put the flag up, the engine starts to receive a significantly larger amount of fuel. At this point, the snowmobile is running at high crankshaft speed. The use of a flag greatly facilitates the operation of the entire mechanism in the cold season: in autumn, winter, early spring, in frost and cold.

Drivers who constantly operate snowmobiles during the autumn-winter season use this device when starting a cold engine in the morning. The mechanism that has cooled down overnight is much easier to start if you raise the flag up. Quick high-quality start-up, accelerated warm-up greatly facilitate the operation of the snowmobile.

After starting a cold engine, the mechanism that has cooled down in the cold overnight should be thoroughly warmed up. The checked box allows you to do this much faster than the standard mode. The snowmobile will work for some time on suction, quickly warm up and you can hit the road.

A well-heated engine runs stably, without pops, jerks, or difficulties. After normal warm-up, the flag goes down and takes the standard position. Then the machine is operated in the usual operating mode.

An engine that has reached operating temperature needs a small amount of fuel mixture for stable, trouble-free operation. In a similar rhythm on a snowmobile, the engine enters an economical fuel consumption mode and can be operated for a long period of time.

Mikuni carburetor adjustment on Buran

Precise adjustment of the air-fuel mixture supply mechanism for the Buran snowmobile engine provides:

• instant start without difficulty;
• stable operation during operation;
• significant fuel savings;
• the best safety of spare parts, accessories, details.

Adjusting the idle speed of the Mikuni carburetor is carried out in the following order:

1. Before starting a cold engine, turning screw 5 sets the throttle to a position so that there is a gap of 2 ... 2.5 mm between the lower generatrix of the carburetor body and the throttle base.

Rice. 3. Mikuni carburetor adjustment.

1. Adjustment screw 4 must first be fully tightened, then unscrewed by 0.5 ... 1 turn.
2. Start the engine, warm up for 2 ... 3 minutes at an average crankshaft speed.
3. When tightening screw 5, it is necessary to set the minimum possible speed of the engine crankshaft.
4. Gradually unscrewing the screw 4, to achieve the appearance of interruptions in the operation of the engine. Slowly twisting, find the optimal position of the screw 4. The engine should run at the lowest possible speed without pops, jerks, interruptions.
5. Check the stable operation of the motor by sharply opening and closing the carburetor throttle. In the case when the power unit stalls and stops from a sharp opening of the throttle, it is necessary to tighten screw 4 by a quarter or half a turn.

The fuel mixture will be rich. In the case when the engine stalls and stops at the moment of abrupt closing of the throttle, it is necessary to unscrew the screw 4 by the same number of turns. The fuel mixture will be lean. If the carburetor is adjusted qualitatively, screw 4 is unscrewed by no more than two turns from the fully wrapped position.

By unscrewing the carburetor adjustment screw by a large amount, they create a poor fuel mixture in operating conditions. With such a free attitude to adjustment, the engine may overheat and the unit may jam.

Mikuni carburetor for snowstorm is an excellent technical solution for a snowmobile. Its installation and operation greatly simplifies the winter chores of the owner. Adjusting the mechanism is easy. It’s better to set it up correctly once, so that you don’t look in all winter later. Owners give only laudatory reviews about this carburetor.

Adjustment, installation of fuel injection is carried out in the fall, it is better before the onset of sub-zero temperatures. Usually every snowmobile owner who has adjusted his unit since the fall, rides without worries all winter. You won't have to adjust until spring.

It can be seen from the article that the described type of carburetor is reliable, durable, unpretentious. The mechanism is simple, without technical excesses, so all reviews about it are only positive. Wide unification, stable operation in any frost. The author recommends installing Mikuni carburetors on snowmobiles, motorcycles, all light vehicles without a doubt. This technique will not fail.

Important: Avoid fakes when buying a mikuni carburetor, see the video on how to recognize a fake:

Carburettors that are most often on a snowmobile snowmobile and their characteristics

Most often, carburetors on Burana were used in the K-65Zh model range, there are also K-62, but it actually does not differ from the 65th. Well, membrane carburetors are probably no longer in operation.

Scheme of the carburetor K - 65ZH: 1. Cover; 2.Throttle; 3. Throttle lift limiter (not available for K65B, K65K, K65Zh, K65P); 4. Throttle lift screw; 7. Screw mixture quality; 8. Fuel-conducting fitting; 9. Handle of the trigger rod (only for K65B, K65V, K65K, K65P, K65S, K65F; for other modifications, pos. 19; 10. Float sinker (for K65A, K65L is absent); 11. Drainage hole (for K65A, K65L is absent ); 12. Dosing needle; 13.3 dosing needle holder; 14. Idling transitional hole; 15. Idling hole; 16. Main system fuel jet; 17. Idle dosing tube; 18. Nozzle (for K65I, K65G, K65Zh, K65K, K65P, K65R, K65S absent); 19. Rope blank; 20. Corrector-concentrator cable guide; 21. Corrector-concentrator piston; 22. Drive cable guide.

K-65 carburetors stood and at the moment also stand on different domestic-made equipment, mainly the difference in components, diffuser diameters, GTZ, ZhHKh and atomizer along with a needle.

Comparative table for the K-65 carburetor

Adjustment of the assembly may be necessary if it does not work correctly or changes in driving style. Based on the reasons, the method of work performed may differ. So with a simple calibration of the part for other operating conditions, it is enough to set the jets in a different position. And if you suspect a blockage in the fuel supply system, the carburetor must be dismantled and cleaned.

The device of the carburetor of the snowmobile Yamaha Viking 540

The carburetor of the Yamaha Viking 540 snowmobile is very simple in design.

It consists of the following parts:

• Float chamber with float and locking needle;
• Fuel jet with atomizer;
• The diffuser in which the fuel mixture is formed;
• Throttle valve, responsible for the amount of air entering the carburetor.

Progress of work with a clogged carburetor

Important! All manipulations with the snowmobile must be carried out in accordance with safety regulations. It is forbidden to perform work near an open source of fire. And to protect your hands and eyes, you need to use gloves and goggles.

1. Initially, all adjacent surfaces and the carburetor body should be cleaned of dirt. The fuel delivery system reacts very harshly to dirt, sand or debris that gets into it. Even a small grain of sand can cause a malfunction and interfere with the normal operation of the motor;

1. Next, you should dismantle the node. To do this, disconnect the air duct and all pipes and fixtures that hold the unit in place;

1. The assembly is disassembled and flushed. Disassembly is carried out by removing the jet, then the cover of the float chamber and the locking needle are dismantled. Next, the throttle valve is removed. Assembly is in reverse order. Wash the knot thoroughly. To do this, you can use clean gasoline, thinner or carburetor flushing agent. And to clean the channels and the jet, it is best to use a compressor or a powerful pump with a nozzle. When cleaning the jet, do not use wire or hard needles. The fact is that the part is made of a soft alloy, which is easy to damage with steel tools, and any damage to the surface can lead to an uncontrolled change in the operating parameters of the power unit;
2. Reassembly and installation of the part on the snowmobile;

1. Setting.

After mounting the carburetor, its adjustment is performed. Basically, it consists in adjusting the idle speed and the fuel level in the float chamber. Also, manipulations with the carburetor must be performed only after making sure that other nodes are in good condition.

For this you need:

1. Remove the spark plugs and check that they are in good condition. If they are flooded or have a strong soot, the part must be replaced.
2. Set throttle actuator free play. The working play should be at the level of 1 - 2 mm.
3. Clean the air filter. The amount of incoming air depends on the condition of the element. It is forbidden to perform idle speed adjustment with a clogged filter.

Idling is adjusted using two screws - one is responsible for quality, and the second for quantity. Initially, all adjustments are made on a cold engine. In the warm state, the final calibration is performed. Quality screw (yellow, made of bronze). To adjust it, you need to completely tighten it, and then unscrew exactly 1.25 turns. Next, you need to warm up the motor and set the quantity screw (white, plastic) to the minimum number of revolutions at which the motor runs without interruption (usually 900 - 950 rpm).

Important! Adjusting the idle speed of the Yamaha Viking 540 snowmobile, after running in or for other operating conditions (riding in the mountains or in severe frost), is carried out purely individually. There is no universal screw position for all conditions!

Note. The idle speed setting is only relevant up to ¼ throttle up. Therefore, to reduce fuel consumption, it is necessary to select less productive jets. But this must be done very carefully, since a strong decrease in the cross section is fraught with a depletion of the mixture and, as a result, frequent overheating of the power unit.

Professional snowmobile carburetor tuning. The carburetor is a device that is used in the power supply system of internal combustion engines and is designed to mix air with gasoline, respectively, a combustible mixture is created, and the carburetor must regulate its flow. There are updraft, downdraft, or horizontal carburetors, but downdraft models are the most common. This was due to certain advantages of such parts in terms of improving the filling of the cylinders with a combustible mixture, which leads to an increase in engine power. They are also more convenient for maintenance and repair.

In short, we can say that a carburetor consists of several main parts: a nozzle with a spray, a float chamber with a float, a diffuser and a throttle. The principle of operation of the carburetor is as follows. First, fuel enters the float chamber from the snowmobile tank, where the float and the shut-off needle resting on it float. When the required height of the fuel level is reached, the locking needle closes the tube, and the fuel supply stops. The fuel is consumed, and the float begins to descend, which, when a certain level is reached, again leads to the supply of fuel to the chamber.

The algorithm of work is not the most complicated, but the repair of a snowmobile carburetor is not limited to simply supporting the functioning of the float in the float chamber. After the appropriate diagnostic steps, you will need to adjust the optimal fuel level in the carburetor. After that, it is worth checking its operation at idle, with the throttle closed. If the initial settings are not the best, it will be quite difficult for you to set them yourself, since during idling the system operates throughout the entire throttle opening range.

Idle speed can be adjusted with a jet, a quality screw, which is located on the outside of the carburetor, and a quantity screw, which is responsible for engine speed. To further adjust the carburetor, you will have to tinker with the throttle at idle, varying the degree of its openness. We will not forget about cleaning, which is also included in the snowmobile carburetor repair service. To do this, you will need to completely disassemble it, thoroughly blow it out, clean it and reassemble it.

To carry out diagnostic work on the snowmobile carburetor and to ensure its high-quality repair, it is necessary not only to have high knowledge in this matter, but also to have special equipment available. Our service center pays great attention to diagnostics and repair. We have all the necessary equipment and are ready to carry out diagnostics and repair of the snowmobile carburetor in a short time.

The carburetor should be adjusted only after checking the general technical serviceability of the engine and the power supply system, the serviceability and correctness of the ignition system adjustments.

To preliminarily adjust the quality of the idle mixture, fully tighten screw 2 (Figure 18), then unscrew it by one turn. When the screw is turned clockwise, the mixture is enriched, counterclockwise, it is leaner.

Idle adjustment screw

Idle mixture adjustment screw

The idle speed adjustment is carried out first preliminary (with the engine turned off), then finally.

For preliminary adjustment, unscrew screw 1 until it comes into contact with the throttle. Tighten screw 1 until it touches the throttle, then, continuing to tighten the screw, ensure a gap of 1.8 ... 2.0 mm (Figure 19) between the end of the throttle and the surface of the carburetor outlet (engine side). For final idle adjustment, start the engine and let it warm up. Then, turning screw 2 in both directions within approximately 0.5 turn from the preset position, set it to the position that provides the highest engine speed. After that, adjust the idle speed to the minimum stable by turning screw 1 counterclockwise to decrease the speed.

ATTENTION

During further operation, it is not recommended to change the position of screw 2. Use screw 1 to adjust the idle speed.

Figure 19 - Checking clearance

Adjustment of the quality of the mixture for the operating conditions of the engine, depending on climatic and other factors, is carried out by rearranging the metering throttle needle in the needle lock. When the needle is raised, the mixture is enriched, when it is lowered, it is leaner.

Changing the carburetor adjustment at low negative ambient temperatures

At ambient temperatures below minus 20°C, the carburetor adjustment must be changed. Otherwise, engine damage may result.

Installing a kit of parts to adapt the snowmobile to high altitude conditions.If you live or operate your snowmobile at altitudes above 1200 m (1200 m), the snowmobile must be equipped with a special carburetor kit to adapt it to high altitude conditions. To do this, contact an authorized dealer.

ATTENTION

Do not change the factory carburetor settings if the snowmobile is operated at altitudes up to 1200 m above sea level.

1. Transmission Maintenance

   Maintenance of the snowmobile transmission consists of making adjustments, checking the condition of the variator belt, tightening the threaded connections, cleaning the external surfaces from dirt and lubricating.

   Variator maintenance.For reliable operation of the variator and increasing the durability of the variator belt, the relative position of the driving and driven pulleys is important.

   The size indicated in Figure 4 (55 ± 0.5 mm) from the end of the fixed drive disc to the end of the fixed driven drive, check with two rulers. If necessary, make adjustments as follows:

   loosen the bolts securing the engine to the sub-engine base;

   by moving the engine, set the required size, parallelism of the engine shaft and the drive shaft of the reverse box;

   tighten the engine mounting bolts.

   Check the condition of the drive belt. If the belt is badly worn

   (belt width less than 30mm) or damaged, replace the belt.

   To remove the variator belt:

   turn on any gear of the reverse box;

   remove the variator cover;

   spread the disks of the driven pulley and remove the belt over the edge of the fixed disk;

   remove the belt from the drive pulley.

   Install the belt in reverse order. Make sure the markings on the outside of the belt are not upside down when viewed from the port side of the snowmobile. This ensures the maximum resource of the variator belt.

   Notes:

   1. Mount the belt only after holding it for a day at a temperature of plus 15 ... 25 ° C or at least 30 minutes at a temperature of plus 50 ° C.

      Installation of the belt in the field is allowed only after it has been kept in the engine compartment for at least 15 minutes after the engine has warmed up.

   To lubricate the drive pulley of the variator and the drive shaft of the reverse box:

   remove the variator cover;

   unscrew the bolt, remove the washer, cover and movable disk of the centrifugal regulator;

   disassemble the weights by unscrewing the nuts securing the axles and weights, and wash the axles and rollers;

   unscrew the bolt from the drive shaft of the reverse box and remove the two washers;

   using a puller, remove the fixed disk;

   remove the variator belt;

   remove the retaining ring, half ring and movable disk of the driven pulley;

   lubricate according to table 4 and install the removed parts in reverse order.

   
   

   Attention!

   Lubrication on the working surfaces of the variator disks is not allowed.

   Reverse box maintenanceincludes checking and adjusting the chain tension, checking the level and changing the oil in the crankcase, eliminating oil leakage through the crankcase connector.

   To adjust chain tension:

   unscrew the fixing bolt of the tensioner and remove the rubber cover of the viewing window;

   put the control lever of the reverse box in the "Forward" position

   
   

   by turning the drive pulley disk counterclockwise until it stops

   tension the chain, turning the disk clockwise - relax. The difference between the indicated positions of the chain should be 1 ... 5 mm (see Fig. 20);

   by rotating the eccentric axis of the tension sprocket, set the required chain deflection. Fix the found position of the axis with a bolt.

   Chain tension can be checked by looking at the backlash of the variator driven pulley. Engage forward gear. Measured by outside diameter

   

   of the driven pulley, the play should be 20 ... 40 mm.

   To flush the reverse box, do the following:

   unscrew the crankcase drain plug and drain the oil;

   put the plug back in place;

   pour into the crankcase through the hole in the cover 1 liter of a flushing mixture consisting of 75% gasoline and 25% MK-8 oil;

   start the engine and, with reverse switching, break in the snowmobile for 10 ... 15 minutes;

   
   

   Rice. 20 - Adjusting the tension of the chain of the reverse box

   after running in, drain the flushing mixture and fill the reverser box with fresh oil in a volume of 350 cm through the hole in the lid3 .

   Check the oil level in the reverse box using a special

   probe through the viewing window. When checking, the bend of the probe should touch the lower edge of the viewing window. In this case, the oil level should be between the control marks on the dipstick.