How the Nikki Carburetor Works

The carburetor has the function of atomizing the fuel, mixing it in suitable ratio to air and supplying the mixture to the engine.

It is therefore an important part which can influence the performance of the engine.

The carburetor is a highly efficient one, of two barrel two step and down draft type, having the following special features.

Main Carburetion System

The fuel flowing out of the passage at the bottom of the float chamber passes through the primary main jet and then mixed with the air comming from the main air bleed to be minute drops and inject into the venturi through the main nozzle.

When the throttle valve is widely open and the engine requires dense mixture gas, the acceleting pump opens its power valve, from where the fuel also flows into the main system.

The power valve begins to operate when the throttle valve opens 48° from full closed position.

Slow Speed System

Passing through the main jet, the fuel passage separate from main line and flows through the slow jet, slow air bleed first, slow economizer, slow air bleed second and inject from the by-pass holes and idle holes.

Accelerating System

Mechanical accelerating pump synchronized with the throttle valve is adapted. When throttle valve is open, the piston rod is pushed up with the linkage, which pushed up the piston through the dumper spring. When the piston is comming down, the inlet check valve closes the out-let check valve opens and the fuel within the pump is blown out from the pump jet by the compressed dumper spring and hits against the side wall of the small venturi to be minute drops, compensating trancient sparseness of the fuel. Ajetting amount of the fuel can be varied with the two holes provided on the pump arm, that is, the inserting positions of the Connecting rod.

Starting System

The choke valve is provided with the spring and installed eccentrically on the normal carburetting device and synchronized with the throttle valve. When the choke is fully closed, the throttle valve opens about 14° from a full close. This
is the best condition to start operation. The synchronization of the choke valve and the throttle valve can be exactly maintained often the engine has started firing.

Power Carburetion System

Same as the normal carburetting function the fuel flowing out of the passage at the bottom of the float chamber passes through the secondary main jet and become minute drops mixing with the air coming from the main air bleed and is blown into the venturi through the main nozzle.

When the throttle valve of the normal carburetor is widely opened and the engine produces high power, the throttle valve of the power carburetor begins to open by the sunchronized linkage.

However, at the top of the power carburetor throttle valve is an auxiliary valve which is not open at aslow speed with aheavy load due to the load of the counter weight connected to the valve shaft even when the throttle valve is open. When the engine change to still higher revolutions, the auxiliary valve open against the loat of the counter weight and the power carburetor starts operation for high power. When the normal carburetor throttle valve is in afull open, the power craburetor throttle valve is also to be in a full open.

Float Chamber

Adjustment of the float level can be done from outside by adding or subtracting the needle valve carrier gasket after removing the float needle valve installed at the inlet connector.
As ventilation within the float chamber is of aair vent method and pressure within the venturi and the float chamber is always constant no matter how suctional registance of the air cleaner varies, fuel consumption can be always econmically maintained.

Updated on 04/27/2022

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