Drive Chain Tuning Tips by Professionals!

Except for scooters and shaft drive models, most motorcycles from small engine displacement (-50cc) to Supersports transmits the driving force from the engine through a drive chain.

It is known that the chain needs to be lubricated with chain oil, but it is also important to check the tightness of the chain, as well as the amount of the chain slack.

 

1. The chain slack also affects the suspension movement!?

The drive chain is the most popular power transmission means regardless of genre such as year and displacement, on-road or off-road. Various chains are used, from the 420 size often used for small motorcycle to 530 size for large motorcycle.

Regular cleaning and lubrication are essential to keep the chain long-lasting, another important thing for the chain is to have proper chain slack. The "slack" here refers to the amount of movement when the chain is moved up and down in the middle of the front and rear sprockets.

There are few opportunities to be aware of chain deflection in case of the bicycle, but why is it very important in case of the motorcycle? One of the major reasons is the existence of the rear suspension. The motorcycle chain is connected to the driven sprocket (rear sprocket) assembled to the rear tires and the drive sprocket (front sprocket) assembled to the engine, and the rear tire moves up and down around the swingarm pivot as the center.

If the center of the pivot shaft and the center of the drive sprocket are on the same line, the chain slack does not increase or decrease even if the rear wheel move up and down because the distance between the front sprocket and rear sprocket remains constant. It is the same theory as a bicycle that does not have an external transmission.

However, since most motorcycle drive sprockets are installed in front of the pivot shaft, the driven sprocket and chain track is made the gap when the rear suspension moves and the tires move up and down. The proper chain slack is needed to absorb this gap.

 

2. It is important that the chain slack remains, even if the rear suspension damps!

The chain slack generally increases if the mileage of a motorcycle increases. When the chain is shaken under the swingarm, it is a sign that the chain slack is too large if it moves up and down largely. The proper amount of the chain slack is described in the instruction manual for each model, and depending on the motorcycle manufacturer, information may be published on the manufacturer's website.

If there is no such information, how do we adjust the proper amount of the chain slack? In the case of bolts and screws, there are times when you feel that you need to "tighten it strongly to prevent loosening". In the same way, you might think that “it may be better to be tighter than to be loose”, but in the case of a chain, too much tightening is prohibited. The difference in the distance between the front and rear sprockets and the distance between the swingarm pivot and the driven sprocket changes the amount of chain slack depending on the shrinkage of the suspension or the position of the rear tire.

The chain slack will be decreased as the suspension shrinks due to the rider's weight and driving condition. In other words, the proper amount of the chain slack can be said to be the state where the chain is not stretched and the chain slack remains even if the suspension is in the full bottom.

If you reduce the amount of chain slack when the rider is not riding on the motorcycle with the feeling that "it’s better to be tighter than to be loose", the tension of the chain becomes stronger as the suspension shrinks. When there is no chain slack between the front and rear sprockets, and there is still space to shrink for the suspension, it will be caused a partially extended "uneven elongation" by excessive tensile force is applied to the chain, and it will be caused a load on the engine by adding a large force to the drive sprocket.

Even if the amount of chain slack is excessive, there is a risk that the chain will jump over the tooth of the sprocket or come off, and there are also some problems such as hitting to the swingarm during acceleration and deceleration, so it is not safe if the amount of chain slack is too much also.

It is important to set the amount of the chain slack within the standard value required for each model.

 

3. The chain adjuster should be adjusted evenly to the left and right.

The amount of chain slack can be adjusted by moving the chain adjuster (chain puller) with the rear tire axle nut loosened. In the case of a motorcycle with a built-in adjuster inside the swingarm, the amount of chain slack decreases when the adjustment nut is turned clockwise and increases when it is turned counterclockwise.

In some models that adapt this type of adjustment mechanism, there is a case that has a “double nuts” to prevent loosening. In that case, you must use two spanners to loosen the lock nut while holding the adjuster nut.

 

▲ When loosening the adjuster nut, loosen the lock nut first while holding the adjuster nut. When tightening the nut, use the reverse method, tighten the adjuster nut first, then after that follow the lock nut. The double nut prevents the adjuster nut from loosening due to vibration.

▲ The lock nut of the double nut are loosened and adjusted. Even rotate the adjuster nut by just turning 1/4 rotation, the amount of chain slack changes significantly. So, make fine adjustments without turning too much at once.

If the axle nut is loosened, you can check the increase or decrease amount of chain slack by turning the adjuster nut. It is important to align the scale position of the swingarm so that the adjustment amount of the chain adjuster is the same on the left and right sides of the swingarm. There are various types of the scale. This motorcycle is the type that is judged by the relationship between the rear end of the long hole of the swing arm and the position of the line carved on the adjuster body.

If you adjust the amount of chain slack while grounding the rear tire without using the center stand or maintenance stand, it may happen that the rear tire will not move smoothly forward when you want to increase the amount of chain slack.

The engraved line of the adjuster is aligned on the left and right sides, but the adjuster nuts is wobbly. If you tighten the axle nut in such a state that there is an play in the adjuster part, the axle shaft may slide while riding. It is important to tighten the adjuster nuts so that it will not loosen after adjusting the amount of chain slack.

4. How to eliminate the looseness of the adjuster part.

Intentionally insert the waste cloth or driver shaft between the driven sprocket and the chain and slowly turn the tire in the forward direction to optimize the position of the adjuster itself, after loosening the chain adjuster nut. If the rear wheels are not floating, push the motorcycle itself slightly in a forward direction, and let the chain bite a waste cloth or driver shaft in between the chain and sprocket. The rear tire will stop when biting a waste cloth or driver shaft, and the reaction will allow the axle shaft to move forward to remove the adjuster play.

Then, the left and right adjusters move forward at the same time, so check again, whether if both positions of the marked line are the same. Check the amount of chain slack in this state, and again adjust if necessary.

When putting your hand close to the chain and sprocket, it is important to pay close attention to avoid getting caught by the chain. In addition, to remove the adjuster play, if you turn the tire at a higher force, it will give a damage to the chain and engine, so be careful when operating this working.

 

The drive chain must have proper chain slack to ensure smooth ride and longer chain life.

If the amount of chain slack is large, the swingarm and chain slider will be damaged, and if the amount is small, the movement of the rear suspension will be hindered. The drive chain slack adjustment is simple but deep.

By understanding why chain slack is important, you will also be able to understand the importance of daily maintenance. Let's do the maintenance that can be done by yourself to maintain the good performance of the motorcycle.

 

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