After replacing the starting spring of a motorcycle repaired, the starting mechanism appeared the phenomenon of sliding teeth.

Empirically speaking, there are generally two reasons for the phenomenon of sliding teeth: one is the wear of the starting gear, and the other is the excessive axial channeling of the starting shaft.

It is understood that the car has no sliding teeth before replacing the starting spring, so the wear degree of the starting gear can be temporarily ignored, and the axial clearance of the starting shaft should be emphatically checked. I analyzed the possible causes, discussed with the fingertip powder, and then he operated according to the discussion.

After decomposition, he measured that the axial clearance of the starting shaft is about 2mm, and whether the axial channeling of about 2mm can lead to the sliding tooth failure of the starting mechanism? The gap appears to be so small that it is hard to believe that this gap can cause slippage.

However, through theoretical analysis, it is difficult to find other reasons, first decompose the engine starting mechanism, carefully observe the operation of the starting mechanism at the same time, repeatedly rotate the starting shaft in the direction of starting the engine, and then artificially move axially to simulate the working situation of the shaft when the engine starts.

After repeated tests, it is true that the starting gear and the starting clutch do not mesh well. With the increase of axial channeling, the phenomenon of sliding teeth does appear.

It can be concluded that although the axial displacement of 2mm feels small, it is enough to cause the sliding tooth phenomenon when the starting mechanism is working at full load.

Here the source of the fault is confirmed, then the rest is to continue to analyze the cause of the 2mm axial channeling.

On reflection, I came up with three possible reasons for this.

First, the axial length of the starting spring is not enough;

The second is that the sealing pad used in the crankcase when assembling the engine is too thick;

Third, the thrust pad on the left side of the starting shaft is missing.

These three conditions can lead to excessive axial channeling of the starting shaft and the phenomenon of sliding teeth. Through on-site inspection, it is determined that the axial length of the starting spring is too short. As long as the side of the starting spring is added with a metal gasket of appropriate thickness, so that the starting shaft can move easily when the engine starts, the fault can be eliminated.

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