A Discontinued Moped Makes it an Essential Tool! Importance of a Special Puller and Holder to Remove the Flywheel

01-6.jpg How to

Ignition systems that send sparks to the spark plugs have been contactless, such as transistor ignition and CDI ignition, since the 1980s, but prior to that, they were controlled by opening and closing contact points. Both the sliding point heel and the point contact point, which interrupts the flow of electricity, were consumable parts and required regular maintenance and replacement. Moped class points are often fitted inside the flywheel and the flywheel must first be removed to reach the points.

Removing the flywheel is not just for engine overhauls.

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A contact breaker generates high voltage to the ignition coil by interrupting the electricity generated by the action of a magnet built into the periphery of the flywheel and an internal coil. This model has the contact breaker inside the flywheel, and although the ignition timing can be adjusted, the flywheel itself must be removed when the main unit is replaced.

The flywheel attached to the end of the crankshaft is a bouncing wheel that smoothes the rotation of the engine, but its role is slightly different for automobiles and motorcycles. While the flywheel for automobiles is located between the engine and the gearbox and is used to interrupt the power, the flywheel for motorcycles differs depending on whether the engine is first mounted vertically or horizontally, that is, whether the crankshaft is facing the direction of travel or straight ahead.

Longitudinally mounted engines on motorcycles are limited to a few models such as BMW and Gold Wing, while most other models, from mopeds to big motorcycles, are equipped with transversely mounted engines. The crankshaft is then orthogonal to the direction of travel, so the flywheel is attached to the side of the body. In this case, the flywheel may be used as part of the ignition system.

Specifically, this applies to models from the moped class to the mid-size class. In addition, many flywheel magneto & point ignition engines from the 1980s and earlier have a flywheel that plays an important role in point intermittence. Spark plug ignition timing is very important to the engine and requires accurate capture of piston movement.

In this case, the angle of the flywheel directly connected to the crankshaft is most appropriate for determining the piston position. In the case of a flywheel magneto type ignition system, the electricity required for ignition is generated by the interaction between the magnet built into the flywheel and the coil fixed to the crankcase, so there is also a rationale for installing the points near the coil.

For these reasons, maintenance of the ignition system is not easy for small exhaust models with contact breakers built into the flywheel. When opening and closing the point contacts, which carry high voltage, sparks fly onto the surface of the points, causing the surface to become rough, and the point cam and point heel, which open and close the points, are worn as they rotate and slide while making contact. Then, as the mileage increases, the timing at which the points open and close gradually shifts, and the ignition timing also changes, resulting in a deterioration of the engine's condition.

When the ignition timing is off, a screwdriver is inserted from the outside of the flywheel to fine-tune the position of the contact breaker so that the timing of the point opening matches the "F" stamped on the outside of the flywheel indicating ignition timing. However, as the point and heel wear progresses, adjustment alone will no longer be sufficient, and the contact breaker itself will need to be replaced.

POINT
  • Point 1: Some motorcycle engine models have an ignition system built into the flywheel at the end of the crankshaft.
  • Point 2:If the contact breaker for point ignition is located inside the flywheel, the flywheel must be removed when the breaker is replaced

Flywheel puller is used in combination with flywheel holder

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Example of a general-purpose flywheel puller. This product has a total of six different threads: M24 x 1.0 and M27 x 1.0 for the cylindrical part and M10 x 1.25, M14 x 1.5, M16 x 1.5 and M18 x 1.5 for the cross handle. That's how many different types of female screws there are on the flywheel side.

 

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When using the male threads on the M24 x 1.0 and M27 x 1.0 cylindrical sections, the flywheel can be removed by placing the M10 x 1.25 tip of the cross handle on the end of the crankshaft and tightening the screw, with the taper engaged tightly.

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A band-type universal pulley holder that is more often used to hold down scooter-driven pulleys than flywheels. As long as the diameter of the band matches, it can also be used for flywheels, but depending on the engine, the handle of the holder may interfere with it and prevent proper installation.

 

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If there is a hole or slit on the outer surface of the flywheel where the pin can stick, a pin-type universal holder can be used. Set the flywheel considering the direction in which the body is set so that the pin sticks out when the flywheel is turned in the loosening direction.

 

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When loosening or tightening the nut at the center of the flywheel, the pin type transmits torque more firmly than the band type because it does not slip. It is common for the flywheel held by the holder to rotate when the nut is turned, but care must be taken so that the pin stuck in the slit does not touch the inner coil or contact breaker and cause damage.

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Tighten the large threaded attach main to the flywheel and hit the cross handle with a hammer. If the flywheel is not stopped at this time, the flywheel will turn at the same time as the handle turns, so a band-type puller is used to hold the flywheel in place. It is more effective to use a hammer to tighten the handle because it is easier to disengage the taper of the mating part if the force to tighten the handle is applied all at once.

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Once the flywheel is removed, the two sets of coils and contact breakers can be removed. In case of long-term immobility, the contact breaker contacts may be corroded or covered with oil, so they should be cleaned with parts cleaner and polished with sandpaper.

To replace the contact breaker inside the flywheel or the condenser that functions as a set with the breaker, the flywheel itself must be removed. The crankshaft and flywheel are tapered to each other and are tightly fitted together by tightening a central bolt or nut. Therefore, the flywheel cannot be removed simply by removing the bolts and nuts; a special tool, the flywheel puller, is required.

Observing the flywheel, there is a screw in the center. When a flywheel puller compatible with this screw diameter is installed and the center push bolt is screwed in, the crankshaft end is pushed and the flywheel is released toward the front. The flywheel side threads come in several sizes, and the versatile flywheel puller comes with several different threads for use with different flywheels.

Here we introduce the case where the flywheel screws are female thread type, but depending on the model, the flywheel side may have male threads and a female thread type flywheel puller may be required.

Furthermore, when using a flywheel puller, a turnstopper must be set to prevent the flywheel from turning together when the puller is tightened. If there is a hole or slit on the outer surface of the flywheel, a pin-type holder should be set to prevent the flywheel from turning, while a band-type pulley holder should be used for flywheels without a hole for a pin.

If you get a discontinued moped model and the spark plug does not skip sparks no matter how many times you depress the kick pedal, you need to check the flywheel and, if it was a points ignition, check the ignition timing and points condition. As a result, remember that you will need a flywheel puller and an anti-turn holder when replacing the contact breaker inside the flywheel.

POINT
  • Point 1: Flywheel screws come in various sizes and require a flywheel puller suitable for the screw size.
  • Point 2: The holder that stops the flywheel from turning and the flywheel puller should be used as a set.
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