DIY motorcycle carburetor synchronization

2024 Author: Erin Ralphs | [email protected]. Last modified: 2024-02-19 11:42

Any experienced motorcycle owner will say with confidence that carburetors must work in synchronous mode. The opposite is evidenced by engine vibration, increased fuel consumption and swimming at idle. Synchronization of carburetors on a motorcycle is required every 6000 km. Many advise to carry it out before the start of the season or after purchasing the bike.

When is it necessary to synchronize carburetors on a motorcycle?

Characteristic signs of desynchronization of carburetors is the occurrence of typical vibrations during engine operation. Uneven heating of the cylinders is another symptom that eloquently indicates the need for maintenance. The reasons may be different: contamination of the fuel system, uneven wear of parts, as well as the fall of the motorcycle and wear of the drives.

Manufacturers strongly recommend that the carburetors on the motorcycle be synchronized every 5,000-6,000 km. Besides this, there issome more points that may signal the need for cleaning and synchronization. They are listed below:

• wear on both cylinders;
• cleaning the carburetor;
• blockage or contamination of the fuel system;
• motor vibration;
• motor repair or replacement;
• repair or replacement of the gas distribution system;
• replacement of components of the piston group.

All of the above problems can occur due to low-quality fuel, extreme driving or improperly selected filters. Leaving the motorcycle for long periods of time with gasoline in the tank can also cause carburetor failure. This is why experienced motorcycle owners recommend synchronizing before the start of the season.

Failure symptoms

There are characteristic signs that eloquently indicate a malfunction of the node. These include:

• increased fuel consumption;
• drop in acceleration dynamics (motorcycle doesn't pull);
• deceleration and the presence of backfires, which, in turn, is fraught with consequences for the piston system.

Synchronizing carburetors on a motorcycle with your own hands is not such a difficult process if you approach it correctly. Anyone who is able to independently change the oil or fill in antifreeze will be able to synchronize the carburetors. The main thing is the presence of a special tool, or rather, a device.

Synchronizer

What is a special device designed to synchronize carburetors on a motorcycle? In fact, this is a block consisting of two or four vacuum gauges. It is not worth trying to assemble such a unit on your own, since these devices, as a rule, must be set to a vacuum that corresponds to it in the intake pipes when the engine is idling. In addition, these instruments must be calibrated in such a way that the readings are absolutely identical at equal vacuum.

By the way, branded units have special devices that reduce the vibrations of the arrows when the air flow pulsates in the intake pipes. Yes, true professionals have learned how to calibrate a 4-cylinder engine using 2 vacuum gauges. But an inexperienced self-taught locksmith should purchase a special 4-device synchronizer - this device has higher accuracy, and it will take much less time.

Special attention deserves a device not with a scale and arrows, but with a liquid crystal display - this eliminates the need to monitor four arrows at the same time.

Preparing for synchronization

Throttle actuators should be adjusted before synchronization. To do this, remove the fuel tank from the motorcycle. If provided by the design of a particular model, then the air filter must also be dismantled. Some models provide for the removal of the carburetor block itself. You can connect the measuring pipelines to the VPD through special vacuum ports, which are easily located through the plugs.

Next, you should start the engine, warm it up and adjust the vacuum gauge valves for minimal fluctuations. If you release the valve, the device will begin to respond more to the change in vacuum. When tightened, the vibrations of the hands will be slight.

Synchronization of carburetors on a Ural motorcycle or any other modification must be carried out at a certain speed, the value of which is determined by the manufacturer. This parameter can be specified in the instruction manual.

Special nuances when working with different engines

There is a typical procedure for synchronizing carburetors. However, there are certain features that are characteristic of certain motorcycle models. So, for example, on two-cylinder engines, synchronization is performed using the main screw, which controls the position of the remote sensing of one and the second cylinder. It can be found directly between the carburetors.

For four-cylinder engines, it is best to use a special tool for timing motorcycle carburetors. In this case, in addition to the base screw, two adjusting fittings must be used. The first screw is for controlling DZ in pairs 1 and 2, and the second, respectively, is for controlling D3 in cylinders 3 and 4.

To synchronize and clean motorcycle carburetors, it is necessary to set equivalent vacuum values in the VPD by rotating the screws. ATfirst of all, it is necessary to adjust the first fitting, after which the third screw, and finally the second (central) screw.

Synchronization is considered successful if a sharp increase in speed and their subsequent reset to a certain mode (recommended by the manufacturer) leads the arrows directly to all vacuum gauges to the same vacuum value.

Boxer engine

Incorrect adjustment of carburetors results in an uneven load on the cylinders. What is the risk? Yes, at least by overheating one of them with subsequent replacement. There are several ways to synchronize carburetors on a boxer engine. The first one is recommended by manufacturers:

1. Set the motorcycle on a special stand.
2. Start the engine and shift into fourth gear.
3. Turn off the first cylinder by removing the voltage wire from the spark plug.
4. Increase speed to the speedometer mark of 50 km/h.
5. After the mode stabilizes, simultaneously turn off the 1st and turn on the 2nd cylinder.
6. Achieve the same speedometer reading in both cases by turning the adjusting screws.

This adjustment method is quite complicated and requires long engine operation. That is why it is important to monitor the temperature during the process in order to avoid overheating of the motor.

Adjustment of carburetors on the example of a motorcycle Honda CB400

For thisyou will need a special device and the motorcycle itself. Before starting the procedure, remove the fuel tank. In order to somehow regulate the fuel supply, it is necessary to build a simple device from a plastic bottle and a dropper, one end of which is connected to the fuel hose, and the other is immersed in a bottle of gasoline. It is advisable to hang the container with fuel directly somewhere higher. As a rule, a motorcycle handlebar can be used for this purpose.

It remains only to remove the seat and tank, after which it is necessary to unscrew the screws that are the plugs of the synchronization holes. They are located on the shirt of the extreme right cylinder between the ribs. Middle cylinder plugs are not easy to find, but they are there - you just need to look more closely.

After that, it remains only to unscrew the plugs of the holes and screw the synchronizer fittings into them. Next, you need to turn on the device, start the motorcycle and calibrate the synchronizer. Based on this, we can conclude that the synchronization of carburetors on a Honda CB400 motorcycle is a simple process if you follow the recommendations correctly.

How does synchronization work?

There are 4 adjusting screws between the carburetors. With the engine running and the device connected, pay attention to the readings of the device. First you need to tighten the first screw, while adjusting the operation of the first two cylinders. After that, tighten the second screw, synchronizing the work of the 1st with the 2nd and 3rd with4th cylinder. The third screw will allow you to adjust the operation of two pairs of carburetors. Getting to the adjusting screws is not easy. It is convenient to tighten them with open gas.

Synchronization of carburetors on a Yamaha motorcycle is almost the same as the same process, only on a Honda. It's only difficult the first time. Subsequent adjustments will be easier and faster.