How to install SECU-3 automatic choke on the Solex carburetor.

How to install automatic choke on the Solex carburetor.

Well, what else is needed to install the automatic choke on the carburetor besides microprocessor ignition system SECU-3T itself:

– air choke control unit (availability and price are on the page Production),

– stepper motor 2170-8127100 (gear reducer of the airflow distribution).

 microprocessor ignition system SECU USB with MAP sensor +Carburetor auto suction+ gear reducer of the airflow distribution 2170-8127100

The stepper was chosen because of its accessibility and relatively easy installation on the popular carburetors like “Solex” and “Ozon”.

The correct installation of the automatic choke gear on the carburetor should meet the following requirements:

1. The coaxility of the air choke control and the gear reducer rod should be kept. In other words the axle of the gear reducer rod should be parallel to the plane streamer of the air choke control gear.

2. In case of maximal going out of the rod from the engine in the area which is marked on the picture below with number two the rod thread (worm) shouldn’t be conspicuous. If it is conspicuous the engine should be removed closer to the air choke control gear.

3. The gear reducer fixation should be rigid.

auto suction on the carburetor

The hole for a screw should be drilled in a plastic tip of the gear reducer rod for the fixation to the streamer. The washers are used to follow the requirement of point 1.

 auto suction on the carburetor

The stepper motor of gear reducer has four wires of different colors for the connection with the air choke control unit.

They should be connected in the following sequence:

  • green – 1 (SM_OUT1)
  • red – 2 (SM_OUT2)
  • black – 3 (SM_OUT3)
  • white – 4 (SM_OUT4)

The pinout of the auto suction unit

Two outputs should be reassigned (remapped) before the connection to the microprocessor ignition system SECU-3 as follows:

SM_DIR and SM_STEP and should be connected accordingly to DIR and STEP contacts of the air choke control unit. The power supply of the air choke control unit and ground could be taken from the same-name contacts of the microprocessor ignition system SECU-3.

secu-3t connecting ign_out3 and ign_out4 to secu-step

How to connect SECU-STEP to BL and DE pins inside SECU-3T unit (recommended only for experienced users):

secu3t_blde_to_secu-step

Users of the SECU-3 Lite ECU can also connect SECU-STEP to their unit:

Connecting autochoke control unit to SECU-3 Lite ECU

For the carburetor “Ozon” put the inversion mark (check box) on the DIR output. There should be no inversion for the carburetor “Solex”.

(The information regarding the outputs reassignment is available in Manager instructions)

Some more photos of the automatic choke installed on carburetor from other viewpoints:

auto suction on carburetor  auto suction on carburetor  auto suction on carburetor  auto suction on carburetor  auto suction on carburetor  auto suction on carburetor  auto suction on carburetor  auto suction on carburetor

Automatic choke on carburetor video of operation:

In this video you can see that the rod thread goes out of the gear reducer in the extreme position. This is wrong. It is necessary to install the gear so that the rod thread should be not conspicuous.

After the installation and connection we are checking the operation:

Push the button “Test” on the Manager tab “Air Choke Control”.

Test Button SM_CONTROL

The air choke will start to open and close in full stroke. It is necessary to avoid the shimming of the gear reducer rod or other disturbances for its motion as well as going of the rod thread out of the gear reducer housing ranges.

Find more information about the automatic choke adjustment in the first post of this theme in forum