market dynamics
Motorcycle is difficult to start and irregular flameout, how to repair?
Release date:2021.12.16

Recently, I overhauled a pedal motorcycle. After traveling more than 20,000 kilometers, it often appeared difficult to start. After barely starting, it often appeared a rush and a crash during driving. Sometimes there will be sudden and irregular flameout, and the fault is more and more serious.

This fault repeatedly, the owner before also found a number of maintenance shops, check all the motorcycle electricity, gas, oil, has replaced the spark plug, high voltage package, electronic igniter, reed valve and other parts, have not found the root of the fault.

After seeing the broken car, first understand the situation in detail, and then test run. The vehicle will be big support, press the start button several times, the engine reluctantly started, slightly warm the car, fuel door driving, feeling a more obvious phenomenon of a rush.

Turn off the ignition, turn it on, and it's hard to turn it on.

This phenomenon occurs, experienced repairmen will automatically check the oil circuit and circuit, which is the most likely part. In order to prevent oil blockage, first check the carburetor oil level, loosen the float chamber oil discharging screw, put the oil discharging pipe between the carburetor body and the float chamber, the oil level is basically normal.

Remove the carburetor, decompose the float chamber cover, carefully check each volume hole, no blockage phenomenon was found. Complex, with a transparent hose managed to insert the carburetor float chamber with oil hose, and make the pipe mouth up, start the engine at this time, it slowly in the door at the same time observe the carburetor oil plane, not seen a significant decline phenomenon, then remove the negative pressure switch exert negative pressure suction tube, the fuel flow smoothly, the vacuum diaphragm valve is working properly, check the fuel tank cap is no jam phenomenon, It means the failure was not caused by motorcycle fuel lines.

Remove the spark plug, plug the spark plug hole with your finger, step down the starting pedal, there is rapid gas out of the spark plug hole, the compression pressure is normal.

Remove the spark plug and put it on the high pressure cap to test the fire and check its ignition performance. The result shows that blue-white spark is emitted between the spark plug electrodes, accompanied by "snapping" sound, but sometimes there is no fire, indicating that the ignition system has bad contact.

Careful analysis of the fault symptoms of the vehicle, may be the vehicle grounding loose, in irregular contact bad state.

Remove the suitcase and check the ground wire under the starter motor to make sure it is properly connected. When I checked here, I was really stumped. The oil, electricity and gas lines were all normal, but I couldn't find the root of the fault. It was really incredible.

Careful thought some abnormal phenomena of the fault occurs, the engine starts, sometimes different sound will come at the right side of magneto, according to the electric principle analysis, if the trigger coil installation seat loose brush touch and magneto rotor convex block, or trigger the lug pole and magneto rotor gap is big, although there is a spark, but lack of trigger voltage, It will also affect the normal ignition of the engine.

Remove the engine air hood, remove the cooling fan, hold the feeler gauge and check that the trigger clearance is 0.25mm. At this time, my finger accidentally touches the magneto rotor shell as shown in the figure below, and the magneto rotor loosens unexpectedly and the magnetic gap changes. Is the fastening nut of the magneto rotor loosened due to long-term operation?

Use a 14mm socket wrench to check the fastening nut of the magneto, no signs of loosening, and push the magneto rotor shell with fingers to check that the outer circle of the shaft sleeve spline in the magneto rotor shell spline and the inner hole of the magneto rotor shell spline have become loose because of the riveting. Replace the qualified magneto rotor, reinstall the disassembled parts, press the start button, the engine is ready to start, 5 kilometers on the road test, everything is normal, the original car irregular flameout fault is eliminated.

This is a difficult fault. Originally, the magneto rotor assembly is composed of two parts. The outer circle of the shaft sleeve and the inner hole of the magneto rotor shell are connected by triangular splines (the triangular spline has 64 teeth as shown in the figure below.


The inner hole of the shaft sleeve has a semicircular keyway and the left shaft end of the crankshaft is conical (the taper is 1:5). It is positioned by semicircular keys and fastened by the M14mm hexagonal nut. Because the magneto rotor components of triangular spline riveting connection is not very strong, plus and not according to the technological requirements for welding, the triangular spline connection between the two parts have loose after motorcycle driving tens of thousands of kilometers, at the same time by the inertial effect of magneto rotor swing without effective coordination, triangular spline connection is worn and not role positioning.

When the crankshaft rotates, magneto rotor and shaft sleeve can't sync, the magneto shell convex block to trigger and trigger coil rotor magnetic pole position and clearance between the irregular change, not only influence the triggering time of the engine and the trigger signal, also caused the motorcycle and sometimes difficult to start and irregular stall failure, at the same time operating noise.

Through the whole process of troubleshooting this fault, it can be seen that when checking the ignition fault, the general repairman is checking whether the key of the magneto rotor rotor and the left end of the crankshaft is shifted, but he can not think of the spline outer circle of the rotor sleeve and the spline inner hole of the magneto rotor shell is loose due to the unstable riveting, causing the trigger signal to be unstable.

The fault is relatively rare, in this remind maintenance personnel in the investigation of ignition failure, the first to repair the structure of the faulty car electrical parts for a full understanding, the second do not ignore all the impact of ignition parts for careful inspection.