Unlike four-stroke engines, where they have long switched to an electronic injection system, two-stroke engines for the most part remain carbureted. This is due to the fact that a two-stroke engine, even without an injector, is itself quite economical. Therefore, when setting up most devices with them, starting from chainsaws and ending with snowmobiles, you need to know how their carburetor works.
Before adjusting the K65zh Pekar carburetor on the Buran snowmobile, it is best to familiarize yourself with its basic device and operating principles. Its device is much simpler than, for example, the Zhiguli Ozons.
Snowmobile operation, starting performance, fuel consumption and reliability are largely dependent on the correct settings. Adjusting the carburetor on the K65Zh is one of the most important. With a good carb setting, the Buran will drive confidently, consume a bit of fuel and start from a half turn, and if it is bad, it won’t go at all.
K65zh consists of four main systems:
- Float chamber;
- Launch systems;
- Idle systems;
- Travel systems.
Base Model Design
The four systems mentioned above are practically autonomous and can be individually configured and repaired. The work of each of them has little effect on the work of the other. Adjustment of the carburetor on the K65zh snowstorm can be carried out separately for the starting system, idle and working stroke.
At the bottom of the carburetor is a float chamber. In the operating mode, a different amount of fuel gets there, from where, with the help of a suction and a chamber with a needle, the fuel mixture enters the engine under the influence of vacuum. Fuel also enters the float chamber in the event of overflow. So that the vacuum does not form in it during operation, it has a special throttle, through which air enters and the pressure is equalized with atmospheric pressure.
In the center is a chamber in which air is mixed with fuel, and then this mixture is fed into the engine cylinder. It has two shutters with which the mixture is fed into the cylinders. The dampers must be adjusted so that the fuel is supplied equally through both, that is, that they open synchronously and by the same amount.
The start-up system consists of a spring-loaded plunger. In the K65zh model, it is connected to a magneto cable. In others, K65s and “B” motorcycle carburetors, the needle plunger works autonomously. At the time of start-up, the plunger is pulled out, a certain amount of fuel is taken from the float chamber, which is then thrown with force, mixed with air and fed into the engine. In the case when the float chamber is empty, it is possible to operate the plunger as a so-called suction.
The idle system has a separate air intake. It is regulated so that the engine while idling consumes a minimum amount of fuel, while not stalling. The idle system is also used as a warm-up system for the engine. In the old carburetors of four-stroke engines, a separate system was used for this.
It is regulated with just two screws – a mixture quality screw and a mixture quantity screw. Given that warming up and idling of the snowmobile in winter requires more fuel, keep the number screw a little more open than on motorcycle systems.
The travel system is represented by two throttle valves, as well as a fuel supply system. It works under the influence of vacuum, which is formed during the operation of the engine. The vacuum force sucks in the fuel mixture and injects it into the working chamber, mixing with air. Adjustment is carried out using a special needle. The needle has five positions.
Under normal conditions, the needle is set to the third division. When working in the heat, it is placed one or two divisions below. Adjustment of the carburetor for the K65zh snowmobile is done to work in frosty conditions. Therefore, here the needle should be set one division higher, and when working in extreme conditions, for example, at -50 degrees, two divisions.
Adjusting the float chamber, needle, dampers and other systems is quite complicated, for this purpose, you should give the snowmobile for repair so that it is handled by a specialist. Otherwise, there is a risk of being stuck in the cold in the middle of the ice with a broken snowmobile. Only the screws of the quantity and quality of the mixture should be regulated independently, as well as the floater drowner, which should be immersed in the snowmobile when riding in frost.
It is based on mixing the fuel mixture with air when spraying in the carburetor working chamber. This principle works on the basis of a change in pressure with a change in volume. During the working cycle, the fuel mixture is drawn under vacuum into the carburetor chamber, where, once in the so-called. A “funnel”, that is, an expanding chamber, is sprayed and forms an emulsion, which includes gasoline and air. In some cases, oil also enters the funnel, but this is not provided for in this carburetor.
Characteristics of carburetors model K65zh
|Power of the main jet, cubic cm / min||190|
|Idle hole||0.7 mm|
For an ordinary person, these characteristics will not say anything special, except that they will be useful when searching for spare parts. However, for a search it is best to tell the seller a specific carburetor model – K65zh.
The device carburetors model K65zh
As already mentioned, the carburetor itself consists of four systems: a float chamber, a stroke system, an idle system and a start system. However, the device of some systems will be considered in more detail here.
It consists of a needle, the main nozzle of the fuel system, an air supply channel and a spray. All this is part of the working stroke system. Fuel flows through the main fuel jet from the float chamber to the atomizer. The amount of fuel is regulated by a needle, which is placed in one of five positions. The fuel enters the atomizer through the gap between the channel and the needle under the influence of the rarefaction force, which is formed during the operation of the cylinders. One of the main elements for adjusting the K65zh carburetor on the Snowmobile is the needle.
The idling system is responsible for ensuring that the engine does not stall when the clutch is disengaged and the gas released. At the same time, it is required to adjust it so that fuel consumption in the cold is minimal. Adjustment is carried out using two screws – the quantity and quality of the mixture.
A good sign is that the engine starts up confidently from a cold state and does not stall, when the engine warms up, the revolutions increase slightly, and when gas is given, they quickly jump to the maximum value. At the same time, as elsewhere, there is a middle ground. You have to choose – either quickly gas from a place, or spend less fuel.
Start-up is carried out by means of a starting plunger. At the moment of starting with magneto, fuel is sucked from the float chamber through the start hole with a plunger, then it is injected into the diffuser funnel into the start sprayer, which opens on the side of the start hole. After that, the carburetor goes into idle mode, the excess crowd is poured back into the float chamber through the drainage hole.
Installing a new carburetor
It is carried out using fixing bolts M8. Use a special rubber gasket. It is better to finally connect the fuel pipe to the carburetor fitting after full adjustment, before that it is better to start the hose slightly, because then you may need to remove it.
Carburetor adjustment K65zh
Before adjusting the K65zh carburetor on the Buran snowmobile, you need to install it, connect the gas cable to the carburetor lever, and the magneto cable to the start plunger. The throttle should fully raise the throttle, but it should have idle for about half a turn. This is necessary so that when turning the steering wheel with a natural displacement of the hand, this does not affect the gas. In addition, adjusting the K65zh carburetor on the Buran-640 snowmobile may not be necessary, since it puts a slightly different Japanese Mikuni carburetor.
Fuel level adjustment
It is carried out by adjusting the floats in the float chamber. Unscrew the bottom of the float chamber and remove the float. First of all, it is required to check the tightness of the float. He is immersed in water and see if the bubbles have gone. Then look at what level the float is approximately. Normally, it is 13 mm from the bottom of the float, approximately in the middle. The size is measured with a caliper. In the case when this figure is different, bend the tab of the float in one direction or another.
It is carried out using a screw, which is located approximately in the middle of the carburetor body and sticks up. The screw must be locked against accidental rotation by the spring. It is completely twisted and then turned off exactly one and a half turns. On other devices, it can be twisted lower, opening half a turn, but for a snowmobile, when operating in frost, it is required to open one and a half. Enrichment mainly affects high-quality start-up in cold weather.
Adjustment of the quality of the mixture in operation
It is adjustable with a needle. Touching the needle yourself is highly undesirable. It is best to entrust this work to a specialist carburetor.
How to adjust the K65zh carburetor on a snowmobile “Buran”?
Only the quality and quantity of fuel mixture screws are adjusted; floats can also be drowned during start-up. All other problems are best solved not independently, but by contacting a specialist.