Starting device
When starting a cold engine under the influence of a thermostatic bimetallic spring of an automatic starter, air damper 1 (see diagram) blocks the flow of air through the carburetor duct. The throttle valve 3 of the 1st chamber under the action of the pneumatic actuator 2 opens a little through the rod system, providing a significant vacuum in channel 4 of the main metering system of the 1st chamber and enrichment of the fuel-air mixture, which facilitates starting a cold engine.
After starting the engine, the vacuum that occurs in the engine inlet pipeline affects the pneumatic drive 2, which moves the throttle valve of the 1st chamber to the position corresponding to idling. Lever 5 rests against cam 6, actuated by an automatic starting device, which slightly opens the throttle valve of the 1st chamber by the amount necessary to increase the idle speed of the cold engine crankshaft.
When the engine warms up, the vacuum acts on the pneumatic actuator, which slightly opens the air damper.
The system of rods and cams 7, which is driven by the throttle valve of the 1st chamber, opens the air damper 1, which causes depletion of the combustible mixture and ensures uninterrupted operation of the engine.
The scheme of the Keihin carburetor when starting a cold engine: 1 - air damper; 2 - the position of the pneumatic actuator of the throttle valve of the 1st chamber when starting a cold engine; 3 - throttle valve of the 1st chamber; 4 - channel of the main dosing system of the 1st chamber; 5 - throttle opening lever of the 1st chamber; 6 - cam for slightly opening the throttle valve of the 1st chamber; 7 - system of rods, levers and cams for controlling air and throttle valves; A - the position of the levers in the cold engine start mode; B - slightly opening the air damper in the idling mode of a cold engine
Idle system and transition system
Fuel is taken from the float chamber through the main fuel jet 8 (see diagram) 1st chamber, passes through the idle fuel jet 9 and forms an emulsion, mixing with the air entering through the idle air jet 10. The emulsion is supplied to the outlet of the idling system under the throttle valve through the hole regulated by the quality screw 11 (composition) mixtures.
With the smooth opening of the throttle valve 3, the combustible mixture enters the channels of the transition system and enters the 1st chamber through the slots of the transition system, which leads to a gradual increase in the engine crankshaft speed. When opening the throttle valve of the 2nd chamber, the transitional system of the 2nd chamber works in a similar way.
Idle system diagram: 3 - throttle valve of the 1st chamber; 8 - main fuel jet of the 1st chamber; 9 - idle fuel jet; 10 - idle air jet; 11 - quality adjustment screw (composition) mixtures
Main dosing system
Fuel enters the float chamber 12 (see diagram), the fuel level in which is regulated by a needle valve and a float.
From the float chamber, fuel through the main fuel jet 8 of the 1st chamber is sucked into the emulsion tube 13, where it mixes with the air entering through the air jet 14. Then the fuel-air mixture fills the mixing chamber formed by the small diffuser AND the large diffuser 15.
The main dosing system of the 1st chamber has a power mode economizer channel. With a small opening of the throttle valve of the 1st chamber, a significant vacuum is created under it, which is supplied through channel 16 to the economizer piston 17. Under the action of the piston, the channel of the fuel jet of the economizer of power modes 18 is blocked. After that, the fuel enters the 1st chamber only through the main fuel jet.
When the throttle valve 3 of the 1st chamber opens to 3/4, the vacuum in channel 16 begins to decrease, and when the throttle valve 3 is fully opened, it becomes equal to zero. Piston 17 goes down. The piston spring opens the shut-off valve of the fuel jet 18 of the economizer. Through the opened jet, more fuel enters the emulsion tube, enriching the fuel-air mixture.
The throttle valve 19 of the 2nd chamber can be opened under the action of two systems. The cam on the axis of the throttle valve of the 1st chamber blocks the opening of the throttle valve of the 2nd chamber until. until the damper of the 1st chamber opens to an angle of 53°. The throttle valve of the 2nd chamber is unlocked in this position, which allows the throttle valve of the 1st chamber to be fully opened. Another system that provides direct opening of the throttle valve of the 2nd chamber is formed due to the rarefaction, which through channel 20 acts on the thermopneumatic valve pan 21 and on the pneumatic actuator 22, actuating the thrust of the throttle control lever of the 2nd chamber. While the engine is cold, the theriopneumatic valve 21 is slightly ajar and the vacuum does not enter the pneumatic drive 22, blocking the opening of the throttle valve of the 2nd chamber. This prevents too sharp depletion of the fuel-air mixture.
Scheme of the main dosing systems: 3 - throttle valve of the 1st chamber; in - the main fuel jet of the 1st chamber; 12 - float chamber; 13 - emulsion tube; 14 - main air jet of the 1st chamber; 15 - diffuser; 16 - vacuum supply channel; 17 - piston economizer power modes; 18 - fuel jet economizer power modes; 19 - throttle valve of the 2nd chamber; 20 - vacuum channel for controlling the throttle valve of the 2nd chamber; 21 - thermopneumatic valve; 22 - throttle actuator of the 2nd chamber
Accelerator pump
When the throttle valve of the 1st chamber is opened, the lever 23 is set in motion, under the action of which the accelerator pump 24 starts to work. The pump pumps the fuel filling the float chamber into the mixture formation zone through the check valve 25 and through the atomizer 26.
Accelerator pump diagram: 1 - diffuser; 23 - accelerator pump control lever; 24 - accelerating pump; 25 - check valve; 26 - atomizer
Wiring diagram for Keihin carburetor accessories. Wire color designation: B - white; G - blue; Zh - yellow; 3 - green; K - red; Kch - brown; H - black. The first letter indicates the color of the wire itself, the second - the color of the strip on the wire.
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