Why Motorcycle Chain Become Loose & How To Fix It

I. Introduction

The drive chain of your motorcycle transmits the power from the engine side sprocket to the rear wheel sprocket and it’s a critical part of your motorcycle.

A little information on the motorcycle chain may help you to take better care of it. This article has covered the following subtopics:

  • reason why your motorcycle chain becomes loose,
  • can I fix the loose chain of my motorcycle,
  • preventive maintenance for your motorcycle chain, and
  • a few frequently asked questions on the topic.

II. Why does your motorcycle chain become loose (reasons)?

How do you define a loose motorcycle chain? The chain runs through the driver sprocket on the engine side to the driven sprocket on the rear wheel. The chain has a vertical play or movement, and you can check this play by placing your finger on the bottom side of the chain and pushing it up.

The amount you can push it up is the play (looseness of the chain) and it should be within the range specified in your motorcycle owner’s manual.  If the play is more than the specified range the chain is loose.

The reasons for your motorcycle chain becoming loose (slack) can be:

  • Your motorcycle has an arrangement to marginally move the rear axle towards or away from the engine to adjust the loose chain. The fasteners on the rear axle for doing this adjustment may become a bit loose due to the continuous vibration of the motorcycle (especially if you ride on a country road or your motorcycle is old) and make the chain lose (slack). You can inspect the chain tensioning bolts and add a lock nut if it is missing. The lock nut helps to minimize the chain slack.
  • Wear in the links of the chain can be a reason for the loose chain. Play within a chain-link like loose pins can be an indication of a worn-out chain. When you push your motorcycle chain sideways you can judge if the chain is worn out or not. A new or good chain will not have much sidewise play.
  • Another reason for the chain slackness is the worn-out sprockets. The play between the chain and the sprocket teeth can indicate the wear on the sprocket. You can also check each sprocket tooth to examine the wear on it.
  • If you have replaced the motorcycle chain recently, the initial wear between the adjacent links may result in a slight increase in length. When you replace your motorcycle chain it is a good practice to ride for 50 to 100 miles and then correct the chain slack.
  • It is important to maintain the correct tension of your motorcycle chain. If the chain is tight, it tries to stretch itself to drive the rear wheel. This can make the chain wear faster and can gradually result in a loose chain.
  • When you are replacing your motorcycle chain, ensure you are purchasing a chain recommended in the owner’s manual. A wrong chain can create problems including a loose chain.

How to check the slackness (looseness) of your motorcycle chain?

Step 1. Study your owner’s manual and note down the value of allowed ‘drive chain slack’. Your owner’s manual generally mentions the slack value as a range viz. 5 mm to 10 mm or 3/8ʺ to 1/2ʺ, etc.

Step 2. Stop the motorcycle engine and let it cool down. You can place the motorcycle on a raised platform (not mandatory, but it makes your work easier) and on its center stand. If your motorcycle does not have a center stand, you can ask your friend to hold it for you (do not use a side stand). Press the gear shift lever to neutral.

Step 3. Some motorcycle manufacturers specify the location for checking the chain looseness (slack) in the owner’s manual. You can follow the owner’s manual guideline for checking the drive chain slack. Experts suggest checking the chain slack at a midpoint between the driver and driven sprockets.

Push the bottom of the chain upwards using your finger/s and the chain moves up. Your motorcycle chain has two positions now (i) the position when the chain was loose (before it’s pushed up) and the position when the chain is pushed up (no looseness).

You can note the vertical movement of the chain if you do this exercise by using a scale. This recorded distance between the two positions of the chain (before and after it was pushed up) is referred to as drive chain slack and it should conform to the range specified in your owner’s manual.

If the recorded drive chain slack is higher than the recommended drive chain slack, your motorcycle chain is loose (slack) and the looseness can be removed by tightening the chain.

Alternately, if the recorded drive chain slack is lower than the recommended drive chain slack, your motorcycle chain is tight and you can loosen the chain to bring it within the recommended chain slack. Your motorcycle has a facility to slightly move the rear axle towards or away from the engine to adjust the loose/tight chain and you can use it to correct the drive chain slack.

III. Can I fix the loose chain of my motorcycle?

Yes, you can fix the loose chain of your motorcycle in the following steps:

Step 1. To adjust the chain slack, loosen the axle nut slightly (use leverage if you have a short wrench).

Step 2. Your motorcycle has a facility to slightly move the rear axle towards or away from the engine to adjust and correct the drive chain slack. Go through your owner’s manual, learn how to do it, ensure you have the required tools, and start.

You have to loosen the axle and use the fasteners to move the rear axle towards or away from the engine. There will be graduations on the left and right sides of the axle to control this movement. Ensure the movement is symmetrical on both sides.

Measure the drive chain slack after every adjustment and continue this to bring the chain slack within the recommended range. Tighten all the fasteners correctly. Experts’ advice is to maintain the chain slack at the higher allowable range for your safety.

Step 3. Once you have finished the setting of the chain slack, ensure the bolts, nuts, and locknuts are properly tightened. Check for the proper alignment of the rear wheel. Finally, tighten the axle nut to the correct torque (according  your owner’s manual).

The advantages of setting your chain slack as recommended in your owner’s manual are (i) optimization of the performance and power of the motorcycle, and (ii) enhancement in the life of sprocket and chain, and added together it makes your ride smooth.

IV. Preventive maintenance for your motorcycle chain.

  • Make a schedule of cleaning your motorcycle chain, checking and adjusting its slackness, and lubricating it every 2500 to 3000 miles or after every 6 months.
  • Check the chain slack once a month and also before and after a long-distance ride.
  • Always set the chain tension as recommended in your owner’s manual.
  • You can also make the inspection of chain, sprockets, and adjustment of chain tension as a part of your motorcycle’s six-monthly or annual maintenance service.
  • Your attention to your motorcycle chain is very important. Do not neglect it since it is a simple part. It has the potential to disrupt your long ride and can cause serious accidents.

V. Frequently asked questions (FAQ)

1What are the causes for a loose motorcycle chain?
There can be different reasons for a loose motorcycle chain viz. (i) normal wear and tear of the links and pins of the chain over a span (ii) the rear axle might have moved a little towards the engine because of slight loosening of the chain tension adjustment nut (iii) in case of a secondhand (old) motorcycle, the previous owner might have set the chain slack wrong (iv) the links of a new motorcycle chain rub into each other in the initial 50 to 100 miles ride and may result in a loose chain (this is normal and can be corrected) (v) wear and tear of the sprocket teeth, driver, or driven, or both (vi) fixing a wrong chain, etc.
2How can I know if my motorcycle chain is too loose?
Your motorcycle owner’s manual specifies allowable chain slack (upper and lower limit). Clean and lubricate the chain and measure its slackness. Your motorcycle chain slack should always be in the allowed range.
3My motorcycle does not have a center stand, can I adjust the chain on a side stand?
Some people suggest adjusting the motorcycle chain when it is on the side stand. But, it is better if you request your friend to hold the motorcycle straight and then do the chain tension adjustment.
4What should be the gap between two drive chain slack checks?
The advice of the senior riders and mechanics is to check the drive chain slack after a ride of 550 miles (350 miles for off-road riders) and also after every long tour.
5What happens if my motorcycle chain is loose?
The repercussions of a loose/slack chain entirely depend on the extent of looseness. A too loose chain can make an irritating noise or can wound the rider’s leg or can come out of the sprocket. The loose chain coming out of the sprocket leaves you stranded on the road and can lead to serious accidents.

VI. Conclusion

The drive chain is an important part of your motorcycle and it will not let you down if you keep it healthy and take care of it. We Hope, the topics discussed in this article have helped you in understanding the motorcycle chain better.

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