At times it may appear to be showing signs of richness or flooding it is really a lean condition. The trick with carb sizing and choke selection is basically one of choosing a size which provides the engine with the air flow it needs without overwhelming it. It is not needed for race applications and it is not useful for most climates. Smaller chokes make street driving fun. Fuel enters the tower at the bottom of the well and air enters from the top. The common location for measuring fuel depth is in the emulsion tube well as its proper functioning is dependent on this level.
There is one for each throat. The Jets have a fuel inlet hole at the bottom and air inlet holes on the sides. For racing, the smallest choke that gives the maximum power on the dyno is the one to choose. As with all other circuits, the Accelerator Pump Circuit can be matched to the engine by varying the components. Start the engine, the engine will run very slowly more like a tractor.
This closing off prevents the piston from pushing fuel back into the fuel bowl so that the charge goes to the engine. It snaps into the top of the emulsion tube. Use your ear, not a scope or tuning instruments at this point. This will hamper the correct operation and make tuning more difficult than necessary. The Accelerator Circuit design also had a clever feature where slow throttle valve openings do not squirt additional fuel to be shown in more detail further below.
It appears that a 32mm choke is the inflexion point where one should consider choosing a 45mm body over a 40mm body. If your fuel level is different from the person's promoting the ideal settings, then you are wasting your time copying their settings. At higher rpms when the throttle valve is moderately to fully opened, the air fuel mixture becomes too rich as too much fuel is drawn from the main nozzle. Venturi in Carb Throat After selecting a carb size for your Datsun, the next step is to select a choke size. Faster flow generally improves low-rpm torque but requires a smaller diameter choke, higher rpm performance requires the most air flow and a large diameter choke is usually best. If all is still best and smoothest idle then confirm and note the final settings. It is now manufactured in Spain rather than Italy.
This promoted fuel draw and fuel distribution. Throttle Plate Return Spring: 1. The size is embossed on the corrector in thousandths of mm. The use of larger venturi will increase airflow, and larger main gas jets than noted below will be required. These will be discussed later.
A slow press of the accelerator pedal prevents the spring 28 from pushing the piston 26 quickly. The above Main Circuit design is only marginally optimal for being an Ideal Carb. The piston pushes fuel from its chamber towards the ball valve 21 and towards the ball valve 23 Spill Jet. It sometimes is overlooked when replacing parts. The venturi sizes listed below are the sizes supplied by Weber in new carburetors.
It is not at all like a Choke. Mixed air and fuel is green. Apart from the active Accelerator Circuit, the remaining four circuits are passive and fuel is drawn from the fuel bowl through vacuum. The mixture of air and fuel is first pulled through four holes in the holder and then through a complex winding set of passages in the carb body to reach the Idle Enrichment Hole and to reach the Progression Holes. Recheck mixture screw to lean best idle again. A selection of spill jet bleed back holes and pump jets are available. For the present, just focus on the theory of operation.
Slow presses simply bleed fuel back to the fuel bowl. There are a lot of fgures, but they are necessary, so bear with me. Only the fuel level and Idle Jet are at play. A rubber-tipped needle valve will reduce wear and tear. Fuel enters from the bottom and air enters from the side. This very famous high performance carburettor is available as a bolt on kit for the A-Series. Cycle the linkage again to be sure that the linkage comes to close without any assistance.
Progression Circuit Drawings Figure 20. This opens the passage and allows the pressurized charge of fuel to continue on to the Accelerator Pump Jet 24 then out into the engine via the carb throat. Accelerator pumps are composed of several components: piston, rod, spring, and retainer: Figure 27. Simply countersinking flat-top screws and trimming the protrusion is all that is needed. It is confusing as to why this circuit is so complex and configurable for automotive applications, however, Weber carbs are used for many applications and it may be for cold weather vehicles or cold weather marine applications.
The orifice sizes range from 0. In fact it can be a nuisance if it malfunctions. The solution is to simply add more fuel holes near the throttle valve. Its location was chosen to be downstream from the fuel nozzle as the manifold vacuum on the motor side of this valve would otherwise suck the fuel from the fuel nozzle when the throttle valve was closed. In the tuning section below, selecting the correct Idle Jet at cruise will be the first and most crucial step. The problem is that most proclaimed configurations are from un-vetted sources promoting certain settings and component vales that are not accurately verified and most often, subjective. Details of the emulsion tube will be shared later in this page.