Common fault of carburetor: hard starting

Starting difficulty

According to the national standard, under the premise of the correct use of the carburetor to start the thickening device, the pedal or electric starting time is more than 15 seconds, the engine still can not maintain continuous operation as starting difficulties. The reasons for the starting difficulties and the corresponding elimination methods are as follows.

  1. No fuel oil in the carburetor float room

 Carburetor oil intake channel is blocked. The analysis and exclusion steps are performed as follows:

 Open the carburetor float chamber and check if the needle valve falls when the float falls. If the needle valve is not closely combined with the needle valve seat with the float movement, it can be judged that the bonding between the needle valve and the valve seat causes the oil inlet channel blockage. This fault is generally caused by the condensation of gasoline glue between the needle valve and the valve seat. Can be cleaned with alcohol or acetone. Such faults often occur on motorcycles that are not being used for a long time. In particular, the engine plant and motorcycle factory did not put the gasoline in the carburetor float room after installation, in the inventory or sales period is slightly longer, there will be gasoline gel condensation, resulting in the performance failure of the carburetor.

 Remove the float and needle valve, connect the gasoline from the oil inlet of the carburetor, and observe the outflow of gasoline from the valve seat. If there is no gasoline outflow, the oil inlet channel is blocked, and compressed air can be used to blow it from the oil inlet.

In addition, the oil circuit blockage indicates that a large number of impurities into the carburetor interior. The root cause is the failure of the gasoline filter. Therefore, the gasoline filter should be checked while cleaning the carburetor.

  1. Starting and thickening device fails

 The carburetor is designed to improve the starting performance. There are two main structural forms:

Barrier mechanism: the shutter mechanism is a relatively simple mechanical device is generally used for straddling vehicles (such as CG125 motorcycle), can be used to pull the shutter handle to observe whether the movement of the shutter method to judge whether it is normal, this device has less fault.

 Bypass adding system: bypass adding system is classified more, the most widely used is electric heating and manual bypass adding system. Electric thermal bypass thickening system is generally used for scooters. The fault analysis and troubleshooting steps are as follows:

1) 4~5 minutes after the opening of the motorcycle switch, touch the plastic shell of the concentrated valve. If there is heat sensation, the circuit is normal; otherwise, the circuit should be checked. If the interface of the concentrated valve is normal, the concentrated valve is damaged and needs to be replaced.

2) During 0~5 minutes after removing the concentrated valve and connecting the circuit, observe the movement of the concentrated valve piston. If the concentrated valve piston is continuously extended with the spring, the concentrated valve is normal; otherwise, the PTC heating plate in the concentrated valve is damaged, and the concentrated valve assembly should be replaced.

3) Clean the thickening channel on the carburetor body with compressed air. Manual bypass thickening system application mulan 50 and other models. The fault analysis and troubleshooting steps are as follows:

(1) Turn down the starting valve joint, pull the thickened handle switch, and observe whether the thickened pull wire can drive the thickened plunger to move up and down. If it cannot move or the plunger falls, the thickened wire should be disconnected, and the thickened wire should be replaced.

(2) Remove the carburetor float chamber and observe whether the inner diameter of the starting foam tube hole on the float chamber gasket is less than the outer diameter of the starting foam tube due to expansion and contraction. If it is too small, it is necessary to replace the gasket or increase the inner diameter of the starting foam pipe on the gasket, which is generally larger than the outer diameter of the starting foam pipe of 1~2mm.

(3) Clean the thickening channel on the carburetor body with compressed air.

  1. Low idle speed

 The phenomenon of low idle speed is: the engine can start but can not run stably, after a moment that is stalled.

Elimination method: adjust the carburetor plunger adjusting screw, turn in clockwise, increase engine speed; turn out counterclockwise, reduce engine speed. The general engine speed is adjusted to about 1500 rpm (straddle) and 1700 rpm (scooter).

  1. The starting method is incorrect

 Incorrect starting method basically appears in the use of starting and thickening device, and the common incorrect starting methods are:

 Do not use the starting and thickening device. This is caused by the user's poor understanding of the function of the motorcycle, because even the use at room temperature will greatly improve the starting performance.

 The starting thickening device is used throughout the start process (for choke mechanism and manual bypass thickening device). When the starting and thickening system works, the engine provides a very thick mixture. If the thickening device is used during the starting process, a large amount of thick mixture into the cylinder will "drown" the engine, making it difficult to start.

The correct way to use the thickening device is: if the engine still does not operate after 3~4 starts, close the thickening device, and the throttle handle makes the carburetor plunger rise and then start again.

Common fault of carburetor: hard starting