2-Stroke x 50cc is a promising future. Moped Scooter Drivetrain Maintenance [3. Driven Pulley

The diameter of the drive belt, which fits into the V-shaped groove of the pulley, automatically changes in accordance with engine speed, allowing the scooter to automatically shift gears from idling to maximum speed without the rider having to change gears. Moped scooters are often left ridden as a convenient means of transportation, but if the drivetrain is not taken care of, performance will deteriorate. On the other hand, proper maintenance will keep them in good condition. Following the drive pulley and centrifugal clutch, this article describes the maintenance of the driven pulley.

The driven pulley works in conjunction with the drive pulley.

The drive system of a scooter automatically shifts gears by means of a drive pulley attached to the end of the crankshaft, a driven pulley leading to the rear tire, and a rubber drive belt connecting them. The drive belt, which fits into a V-shaped groove on the drive pulley, is deep in the groove near the center when the engine is stopped and moves outward as the drive pulley moves closer to the pulley face as the engine speed increases. The diameter of the belt on the driven pulley side changes from large to small in conjunction with this movement, resulting in a change in the reduction ratio and an increase in speed. Since the driven pulley is not connected to the engine, it cannot change its width by itself. However, because it is connected to the drive pulley by a drive belt of constant length, if the diameter of the belt on the drive pulley side changes, the diameter on the driven side must also change. If we observe the relationship between the pulley and the belt from a different perspective, drive pulley The width of the V-shaped groove on the pulley changes → the rotating diameter of the belt changes driven pulley The diameter of the belt changes → the width of the V-shaped groove on the pulley changes, and the driven pulley is dependent.

Remove dirt from the pulley surface that interferes with smooth gear shifting.

The change in the width of the V-shaped groove of the driven pulley, which rotates while being pulled by the drive belt due to the driving force of the drive pulley, is basically controlled by the tension of the center spring. If the spring tension is strong, the V-groove of the driven pulley does not widen even if the engine speed increases = the rotating diameter of the belt on the drive pulley side increases, and the diameter of the belt on the driven pulley does not decrease easily. This is the same situation as in a manual transmission car, where the engine rpm becomes higher when shifting up to a higher gear. Also, when the throttle is released at high speeds, the strong spring quickly narrows the V-groove and the car shifts to a lower speed. While the center spring plays an important role in setting the shifting characteristics, it is not considered to be effective in small-displacement or stock-engine vehicles, and its replacement is not significant in drive train maintenance. What is more important is the smoothness of the driven pulley and pulley face surfaces over which the drive belt travels. As the drive belt rotates between the V-shaped grooves of the pulleys, the sides of the drive belt wear, and some of it adheres to the pulley surfaces. Rust can also form on the pulley surfaces if the belt is left unattended for a long period of time, and running the car in this condition can inhibit smooth gear shifting and cause the belt to wear out. Therefore, when maintaining the drive system, it is necessary to check not only the deformation and wear of the weight roller of the drive pulley, but also the surface of the driven pulley. In this live DIO, the tooth pattern on the cross section of the belt was clearly transferred, so we removed the dirt with sandpaper.

The torque cam, which is difficult in principle, checks for pin wear.

A mechanism that is built into the driven pulley along with the center spring is the torque cam. This consists of a guide groove in the center of the driven pulley face and a guide roller. The torque cam acts like a downshift in a manual transmission or a kickdown in an automatic transmission when the vehicle is approaching a hill from a flat surface or when further acceleration is desired while traveling at a constant speed. Normally, if the drive pulley speed = engine speed, the V-groove width of the driven pulley is also constant, but when the torque cam acts, the V-groove width narrows while the engine speed is maintained, and the drive belt is pushed outward to provide powerful acceleration. In customization or tuning, the kickdown characteristics may be modified by changing to a torque cam with a different guide groove angle, but there is no need to change the torque cam for maintenance on a stock car. However, the guide rollers that slide in the guide grooves must be checked and replaced if they are worn or worn out. Oil on the pulley face is strictly prohibited as it can cause the drive belt to slip, but adequate lubrication is necessary between the guide groove and guide rollers, which slide with strong force. O-rings are also attached above and below the lubricated area to prevent grease leakage, so make sure that the O-rings are not damaged when applying grease.

Check also the clutch outer where the centrifugal clutch lining contacts!

After cleaning the driven pulley and greasing the torque cam, the centrifugal clutch, for which new parts were procured last time, is assembled and the thin nut is tightened. To tighten this nut, the center spring, which has a strong tension, must be pressed against the clutch assembly while carefully setting it so that the nut, which has few threads, will not be gnawed. Tighten the nut firmly so that it does not loosen, as it will cause serious trouble if the nut falls off while driving. The last clutch outer to be installed on the driven pulley side should be checked for dirt and damage on the inner surface where the clutch lining contacts. This live DIO had spot rust on the lining contact area, so we scraped it off with sandpaper to make it smooth. If the surface remains rough, it will cause damage to the lining, and the new clutch that has been replaced will be half as effective. Scooters may seem to have fewer maintenance parts than sport bikes, but you will find that there are many items to check regarding the drive train. Before you panic one day and say, "Oh, it stopped working! it is a good idea to understand what symptoms may occur over time before panicking.

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