1）carburetor abnormal sound diagnosis
1, carburetor tempering sound
The tempering sound occurs in two situations. One is that during startup, the air filter gives out a "pop" sound and emits a stream of white smoke, and the engine is difficult to start. The other is the engine working suddenly from the air filter issued a "pop" sound.
The reasons for tempering carburetor when starting are as follows:
(1) the mixture is too thin;
(2) premature ignition time;
(3) weak spark of spark plug;
(4) the contact gap of the breaker is not correct;
(5) water in oil;
(6) the oil road is blocked;
(7) the intake valve of the four-stroke engine is burnt out, and there is no clearance between the intake valve and tappet.
When the engine is working, the carburetor suddenly backfires. The reasons may be as follows:
(1) the engine load is too heavy and the gear is not reduced in time;
(2) capacitor damage or poor contact;
(3) the oil road is blocked so that the mixture is too thin;
(4) the intake valve of a four-stroke engine suddenly bites to death.
2, carburetor throttle knock
The throttle keeps moving up and down in the mixing chamber. Due to excessive wear, the gap is too large. During the engine's intake stroke, due to the impact of airflow, the throttle generates radial swing and hits the mixing chamber. This sound in the idle branch turn almost can not hear, throttle to 1/4 of the open degree when the sound is the largest, then increase the throttle, the sound gradually decreased, when the throttle to the bottom, the sound disappeared.
When checking, use the screwdriver to listen to the carburetor. When the throttle is added to 1/4 open, there is an obvious knocking sound. Can also remove the air filter, with the finger against the throttle, knock sound disappeared, relaxed finger knock sound again, can be determined as the throttle knock sound.
2）Analysis and elimination of carburetor oil leakage fault
1, float damaged or immersed in gasoline
Cause: float damaged or immersed in gasoline will make float weight and buoyancy change, resulting in oil level rise, resulting in oil leakage.
Elimination method: replace the float.
2, needle valve and valve seat contact surface adhesion foreign matter
Reason: needle valve and seat is to control the amount of oil intake, its sealing requirements are strict, contact surface smoothness is high. If there is a foreign body attached to the contact surface, it will lead to loose seal between needle valve and valve seat, resulting in oil leakage. Foreign matter mainly refers to the impurities in gasoline and condensation gum. Therefore, to avoid such failures, the user should pay attention to regularly clean the gasoline filter and use good quality gasoline. Maintenance and
Elimination method: clean carburetor
3, float hair card
Reason: (1) float by gasoline long-term immersion expansion deformation and float chamber wall contact. (2) float pin and body float pin hole after a long period of friction gap expansion, resulting in contact with the float chamber wall. The float clip prevents the needle valve from returning to its proper position, leading to oil leakage. Maintenance knowledge
Elimination method: (1) if the float deformation is replaced by the float. (2) if the float pin outer diameter wear becomes smaller replacement float pin, such as the body float pin hole wear becomes large, can only replace carburetor assembly.
4, needle valve wear
Reason: (1) needle valve in the process of use due to a long time by the oil contained impurities in the erosion and contact with the seat wear (float buoy two ends of the adjustment imbalance, driving needle valve side force and wear. Needle valve wear causes leakage due to loose seal with seat.
Elimination method: (1) replace needle valve, and the user should pay attention to regularly clean the gasoline filter and use good quality gasoline. (2) replace the needle valve, and adjust both ends of the float buoy at the same level.
3）, carburetor maintenance
1. For plunger carburetor, first remove the carburetor top cover, take out the throttle valve, and remove the throttle wire from the throttle valve under the condition of squeezing the spring with your finger. Remove the pin clip, remove the main oil needle from the throttle, hold it with your finger, and check the cone surface of the main oil needle for wear. Excessive wear here may cause excessive concentration of the main oil mixture.
2. For the vacuum diaphragm valve carburetor, unscrew the vacuum chamber cover screw, remove the vacuum chamber cover, spring and vacuum plunger combination from the carburetor, and check whether the vacuum plunger moves smoothly and unscreeching in the carburetor. While holding the main oil holder, turn the main oil holder to the left and remove it. Remove the spring, spring regulator, main oil needle and gasket from the vacuum plunger assembly (for individual carburetors, please note that the spring regulator and main oil needle seat are integrated).
3. When cleaning the carburetor body and various orifice, compressed air must be used. Never wipe the carburetor and its parts with cloth that is prone to fluff or lose silk, in case the falling particles remain in the place that cannot be seen by the naked eye and cause unexpected failure.
4. For the blocked orifice, it is strictly prohibited to force dredging with rigid objects such as steel wire, so as not to change the aperture of orifice, resulting in the change of carburetor performance, only gasoline and compressed air can be used for flushing.