Hello, dear readers. We continue to study motorcycle-type carburetors. In the previous publication, we got acquainted with the main issues of the formation and ignition of a combustible mixture. Today we will study the main dosing system, consider its operating principle and adjustment methods.
What kind of carburetor is used on the Izh Planet-5 motorcycle
The latest Planet model was produced in several variations. Early transitional models were equipped with K-62I carburetors. Then they began to install the K-65I and the more progressive K-68I with a cylindrical throttle valve.
All three carburetors: top left - K62I, top right - K68I, bottom - K65I
All three carburetors have a similar operating principle. From the tank, through the fuel valve, fuel enters the float chamber. The floats are made of petrol-resistant lightweight material. As soon as gasoline fills the chamber, the floats will float up and the shut-off needle will block the fuel supply channel.
From the chamber, fuel enters the atomizer through the main fuel jet. In it, the fuel is mixed with air entering through a special hole in the atomizer body. The finished mixture enters the mixing chamber (diffuser) and then into the engine cylinder. This dosing system is called the main one. And it only works at medium and high engine speeds, when the throttle is raised more than 2/3 of its stroke.
To operate the engine at low speeds, the carburetor is equipped with an idle system. It consists of a fuel tube, mixture quantity and quality screws, a special air channel, transition and idle holes in the diffuser.
The fuel rises through the tube due to the vacuum in the mixing chamber and is mixed with air entering through the air channel. As a result, the resulting mixture, when the throttle is opened slightly, exits through the idle hole (it is specially located behind the throttle valve, at the end of the diffuser).
If you continue to raise the throttle, the vacuum will increase in the area of the transition hole and the mixture will also begin to flow through it. In general, when you lift the throttle (turn the throttle lever), the mixture becomes leaner and the engine speed increases. The air flow speed increases and, by lowering the pressure in the mixing chamber, the fuel supply increases.
The carburetor of the Izh Planeta-5 motorcycle also contains an engine starting and warming up system (to facilitate engine starting in the cold season). The enrichment corrector is installed on the carburetor body or brought to the motorcycle handlebar using a cable. When it is lifted, 3 channels will open in the carburetor body. Through the fuel channel from the float chamber, the fuel will enter a special cavity, where it will mix with air coming from the air channel (this channel is usually located at the end of the diffuser on the air filter side).
As a result, the finished mixture will flow through a special channel to the outlet of the mixing chamber (behind the throttle valve). The channels are designed in such a way that the finished quality of the mixture is sufficient to warm up the engine.
Float stopper or additional starting device. When you press it, the floats lower and additional fuel enters the chamber. When starting, the mixture is richer and the engine starts easier. It is recommended to use the drowner only at temperatures of +5 C and below.
Operating principle of the main dosing system
The needle moves inside the calibrated part of the atomizer and at low throttle lifts the cross section through which fuel is sprayed is small. As a result, fuel consumption is also low, which is required to maintain the correct mixture composition at low elevations. At higher throttle lifts, the conical part of the needle with a smaller diameter appears in the fuel spray zone, thereby increasing the flow area of the nozzle. This allows you to increase the fuel supply, as is necessary for normal engine operation. This design and the corresponding operating principle of the main metering system makes it possible to maintain the desired mixture composition, so the engine is able to operate correctly at any throttle position.
Interaction of the needle with the sprayer
Now that the principle of operation has become clear, the principle of adjusting the main dosing system becomes clear. Adjustment is carried out using a needle and a calibrated nozzle hole.
Adjusting the K-68 carburetor on the IZH Planet-5 motorcycle
The K-68I carburetor was installed on the Izh Planet-5 motorcycle more often than others. With proper setup and proper care, the motorcycle starts quickly, runs smoothly and without complaints.
To adjust the K-68I carburetor you will need a flat-head screwdriver, pliers, and a ruler. For clarity and ease of adjustment, use the K-68 carburetor diagram.
Algorithm for adjusting the Izh Planeta-5 carburetor:
- The first step is to check the fuel level in the float chamber. Unscrew the camera cover bolts with a screwdriver and remove it. Turn the carburetor over and use a ruler to measure the distance from the carburetor body to the top edge of the floats. It should be 26 ± 5 mm. If the parameters deviate, the tongue of the floats is bent in the appropriate direction using pliers. At the same time, in no case should the parallelism of the floats be disrupted.
- Set a gap of 2 mm between the throttle valve and the bottom of the mixing chamber by adjusting screw 11. Then check the position of the throttle needle. The required needle position is the middle groove. The remaining grooves are made to move the needle lock and adjust the appropriate fuel quality depending on climatic conditions.
- After all the above steps, we proceed to the most important stage - setting the idle speed. The idle quality adjusting screw 15 (located vertically on the left side of the carburetor) is screwed in until it stops, and then unscrewed 1-1.5 turns. Start the engine and warm up for 5 minutes. Using the mixture quantity adjustment screw 11 (located horizontally on the left side of the carburetor), we set the minimum stable engine speed. At the same time, slowly unscrew screw 15 until the engine speed stops increasing. It is the moment of reducing the crankshaft speed that will be optimal for determining the position of the adjusting screw 15. We again reduce the engine speed with screw 11 and unscrewing screw 15, we find a new optimal position of the throttle valve. This operation must be repeated until the minimum, but at the same time stable, engine crankshaft speed is established.
- By sharply turning the throttle lever at idle, we check the correctness of the adjustment (the quality of the mixture). If, when the throttle is opened sharply, the engine stalls or picks up speed poorly, screw 15 needs to be tightened a little, thereby enriching the mixture. If the engine stalls when the throttle is closed, screw 15 should be unscrewed slightly.
- You can also check the correctness of the adjustment by the color of the central insulator of the spark plug. After adjusting the carburetor, drive a motorcycle for a distance of 5-10 km and remove the spark plugs from the cylinder head. Dark carbon deposits indicate that the mixture is too rich. A light color (whitish or sandy) indicates that the mixture is poor. The normal recommended candle color is brown or brick.
- It is also worth remembering that the free play of the throttle cable is 1-3 mm. If it is not there, the throttle adjustment will be incorrect. The free play is set by adjusting a special bolt located under cap 18.
The video below clearly shows the adjustment of the K-68I carburetor on the Izh Planet-5 motorcycle.
Float chamber
The float chamber is attached from below to the body using screws. The joint of the parts is sealed with a gasket made of special cardboard. The float consists of two elements mounted on a common axis. The fuel supply to the chamber is controlled by a needle. The lower part of the needle is connected to the plate on the float mechanism, and the upper part is connected to the fuel supply channel. The movement of the float is transmitted to the needle, which opens and closes the fuel supply to the float chamber. By changing the degree of bending of the plate, you can change the fuel level in the float chamber.
Additionally, the needle has three fixed positions for different operating conditions. At high ambient temperatures (plus 35 degrees and above) and at altitudes of 2000 meters above sea level, the needle is placed in the lower position. At low temperatures - to the upper.
Carburetor repair
When using the motorcycle for a long time, you may encounter carburetor overflow (leakage from the drain hole). First of all, it is recommended to check the fuel level in the carburetor and the tight fit of the shut-off needle. By bending the locking needle brackets in the desired direction, we adjust the fuel level (the distance from the plane of the middle of the floats to the edge of the carburetor body is 13±1.5 mm). The tapered end of the locking needle is made of rubber. If it becomes leaky, it is recommended to replace it with a new needle from the repair kit. It also happens that the floats begin to leak gasoline due to fatigue of the material. It can also be treated by replacement.
Floats
Fuel nozzles become clogged due to low-quality fuel or when dirt gets in from the air through the filter. To clean gasoline, in addition to the mesh in the fuel tap, you need to additionally cut the fuel filter into the gas hose. The air filter must be tightly connected to the carburetor. At the same time, you cannot change its design, much less install a so-called zero.
The filter element must strictly comply with the throughput recommended by the motorcycle manufacturer. Never use needles or wire to clean the jets. It is enough to wash them in gasoline and blow them with compressed air.
Carburetor K-62 disassembled.
Sometimes it happens that when starting or running a motorcycle, the carburetor sneezes. This happens due to problems in the ignition system. The first step is to replace the spark plug. If this does not help, then the ignition has failed. Usually the carburetor shoots during early ignition. Sneezing can also be caused by a mixture that is too lean. The combustion process of such a mixture is slow and when the piston opens the inlet window, the mixture shoots into the diffuser.
The main reason for a lean mixture is air leaks in the following places:
- from under the crankshaft oil seals;
- cylinder heads;
- at the junction of the carburetor flange and the cylinder pipe.
We try to find and eliminate the cause of air leaks using the elimination method. You should start with inspecting and adjusting the ignition system.
Starting device
Almost all versions of the K-62 carburetor were equipped with a starting device. It was cable driven from a rotary lever on the motorcycle handlebar. Additionally, for starting at temperatures below minus 15 degrees, there is a push-button float suppressor. With its help, additional enrichment of the mixture is achieved, which is very important when starting cold two-stroke engines. Such a device was not installed on outboard motor carburetors.
To prevent the engine crankcase from being filled with fuel and getting it in liquid form into the cylinders, there is a drainage channel in the float chamber.
To limit the speed during the break-in period of the motorcycle, a throttle limiter is used in the carburetor. After running in it is removed. The landing flange of the K-62 carburetor is identical to previous models, which allows it to be installed instead of older models without modifications.
Which carburetor is better to put on Planet 5 instead of the original one?
If desired, imported Japanese Mikuni carburetors with diffuser diameters of 30 and 32 mm can be installed on Izh Planet-5 motorcycles. Naturally, you need to select jets recommended by the manufacturer. On Planet-5, the throughput of the main fuel jet corresponds to 270 ml/min, the corrector fuel jet is 255 ml/min.
You will also need to select an adapter to connect the carburetor flange to the cylinder. You can order an adapter from a turner or select one from other motorcycle models. The inlet window of the diffuser on Mikuni is wide, so the rubber pipe for connecting to the air filter will also need to be selected.
It is important to remember that all connections must be tight, without distortions.
The diameters of the diffuser and the cylinder inlet must be the same and have no steps that prevent the mixture from entering the combustion chamber.
This is what the installed Mikuni carburetor looks like on the Izh Planet-5 motorcycle.
All of the above also applies to the installation of a Chinese PZ 30 carburetor on the Izh Planet-5 motorcycle. Its special feature is the presence of a version with an accelerator pump, which helps enrich the mixture at high engine speeds. But to use it, you need an additional cable that will work in tandem with the motorcycle’s gas handle.
With minor modifications, the carburetor flange fits well with the mountings to the cylinder pipe. An important point is that you need to install a rubber or textolite gasket between the pipe and the flange so that the carburetor does not heat up when the engine is running.
This is what the installed PZ30 carburetor looks like on the Izh Planet-5 motorcycle.
Imported carburetors are good because they do not have the usual suction. To start the motorcycle, you do not need to fill the crankcase with gasoline; you just need to open the enrichment corrector. These carburetors also have regular drain holes instead of a drain hole, which are fitted with hoses that can be taken out to any convenient place. For example, under a motorcycle engine, so that if the carburetor overflows, nothing will get dirty.
Modifications
Various versions of the K-62 carburetor were used on two-stroke motorcycle engines of the Minsk and Izhevsk motorcycle plants, on boat engines of the Neptune series, and on Tulitsa scooters. Since the operating conditions and engine sizes of these machines are different, each carburetor had different diameters of the diffuser and fuel supply nozzles, which was reflected in the model index:
- K-62 with a 30 mm diffuser was used on the Jupiter 4 IZH.
- K-62B with a 32 mm diffuser was used on the Planet 4 IZH.
- K-62V with a 26 mm diffuser was used on Voskhod 3.
- K-62G with a 26 mm diffuser was used on Tulitsa scooters.
- K-62D with a 28 mm diffuser was used on the Jupiter 3 IZH.
- K-62E with a 30 mm diffuser was used on Serpukhov motorized strollers.
- K-62P with a 32 mm diffuser was used on the Planet 3 IZH.
- K-62L with a 26 mm diffuser was used on the Neptune 23 outboard motor.
- K-62M with a 32 mm diffuser was used on IZh PS.
- K-62S with a 26 mm diffuser was used on the Minsk 3.115 motorcycle.
Carburetor of Izh Planeta 3.4 motorcycles
Izh Planet-3 motorcycles were equipped with K-62P and K-36I carburetors. The latter had a unique design for its time. The throttle shape was U-shaped, which made it possible to significantly reduce the dimensions of the carburetor (in comparison with the K-28 and K-37 produced at that time). The corrector was moved out of the diffuser area and regulated not the air, but the fuel. This solution made it possible to reduce fuel consumption by 4-6% due to more stable mixture adjustment.
The mixing chamber cover was fastened with special locking springs, which made it possible to quickly and conveniently replace the throttle cable or rearrange the needle. The main fuel jet was screwed into the bottom of the carburetor next to the drain plug. To clean it, it was not necessary to dismantle the carburetor. The diameter of the diffuser of the K-36I carburetor at the outlet is 28 mm, and in the middle it is 26 mm. That is, the mixing chamber is a kind of aerodynamic profile, which has a beneficial effect on mixture formation.
Another feature of the K-36 carburetor is its operating principle, which is similar to a car carburetor. The screw for the amount of mixture in it regulates not the air, but the fuel emulsion entering behind the throttle. Due to this, the sensitivity of the carburetor settings at idle has increased. Adjustment is carried out with screw 1 for the quantity of the mixture (at an angle) and screw 2 for the quality.
The K-36 carburetor has one drawback. It is sensitive to road dust. The upper latches do not seal the lid of the mixing chamber tightly and dust particles get there, the valve begins to jam and wear out. That is why motorcycles on which such carburetors were installed (Kovrovets, Izh Planeta-3, etc.) were equipped with carburetor protective covers.
Later, new K-62 carburetors with the indices I, P, B began to be installed on the Izh Planet-3, 3-01 and 4 motorcycles. The power of two-stroke engines grew and there was a need to increase the diameter of the diffuser (now it was 32 mm), throughput jets, etc.
The new carburetor design made it possible to uninterruptedly supply the engine during sudden braking and acceleration, tilting and rolling of the motorcycle.
Setting up such a carburetor is carried out similarly to the K-68 setting described above. The quantity screw is not located on the side of the carburetor, but in the upper part.
Prerequisites for the creation of K-62
In the USSR, when producing any equipment, unification of components and parts was widely used. Carburetors were no exception. The K-62 carburetor began to be produced in the mid-1970s (Leningrad Carburetor and Valve Plant) named after V.V. Kuibyshev and replaced the K-36 series.
One of the main reasons for the creation of the new model was the increase in engine power. Such engines required enlarged air channels to prepare a larger volume of working mixture. The existing carburetor models did not allow for larger channels, and they also lacked many advanced solutions. The new K-62 carburetor was equipped with a centrally located float chamber, a flat throttle valve, and the float design was changed.
Thanks to such innovations, it was possible to reduce the dimensions of the carburetor and ensure stable engine operation during sudden changes in motorcycle driving conditions.
Carburetor of Izh Planet Sport motorcycle
Motorcycle Izh Planet Sport 350. A legend of the Soviet motorcycle industry. Early models of the motorcycle were equipped with Japanese components, in particular a Mikuni carburetor with a diffuser diameter of 32 mm. Thanks to him, the motorcycle's power was 32 hp. at 6700 rpm.
The reliability of the carburetor is explained by the simplicity of the design. The throttle has a cylindrical shape. To drain excess fuel, there is a special plug at the bottom of the float chamber. The carburetor is adjusted using an air screw and an idle screw (similar to the K-68). To make starting the engine easier in cold weather, there is an enrichment lever.
Later versions of the motorcycle began to be equipped with the domestic K-62M carburetor. The engine power with it dropped to 28 hp.
As you can see, different carburetors were installed on Izh motorcycles of the Planet line, but mostly domestic ones. As engine power increased, the characteristics of carburetors also changed. For high-quality and long-term engine operation, it is necessary to inspect and clean the carburetor in a timely manner (every 3000-4000 km). If desired, imported carburetors can be installed on Izh Planet motorcycles. The main thing is to choose the right jets with the required throughput and match the diameter of the diffuser.
Throttle valve
The throttle valve is stamped from brass, installed in the carburetor body and has a U-shaped cross-section. On the air intake side, the damper has a cutout designed to direct the air flow into the engine cylinder. The upper part of the damper is equipped with a rod with a limiter, with the help of which the degree of overlap of the diffuser is limited (to adjust the idle speed). A cable is connected to the damper and goes to the gas handle on the handlebars of the motorcycle. When the gas is released, the damper is returned by a spring.
Checking the settings
After setting the minimum idle speed, you can check how the K-62 carburetor is configured. To do this, the speed is sharply increased and decreased by opening and closing the damper. A properly adjusted carburetor should react sharply to changes in the position of the throttle handle. If there are failures in operation or the engine stalls, then adjustments to the settings are required.
The first method of adjustment is to tighten or loosen the quality screw by one quarter or half a turn. In case of problems with gas supply, tighten the screw. If there are malfunctions in the engine when releasing gas, the screw is unscrewed. If this method does not help, then it is necessary to re-adjust the carburetor from the very beginning.
We examined the design of the K-62 carburetor and the main points regarding its adjustment. We hope this information was useful to you.
