Paying close attention to the chain and sprockets by ensuring the proper chain adjustment, as well as maintaining proper chain alignment is important and something that anyone who rides a dirt bike should be able to do confidently, as staying on top of the final drive with routine maintenance can have quite a bit of beneficial qualities such as increased power, avoiding broken engine cases and DNF's, or any other number of other calamities you may be able to avoid if your chain were to derail.
It's no secret that if you're on the gas towards a huge gap, and you suddenly derail, or break a chain, this can be disastrous, as well as you can imagine what you're going to be up against should you have problems miles from the truck on a woods loop.
Neglecting the chain and sprockets or any related components could leave someone pushing a dirt bike back to the truck which is ever much fun, and it only gets better when faced with sand or a hill.
If you're interested in saving money, and not be left having to replace expensive engine cases, or worry about sending your chain into the cases, potentially locking up the rear wheel and causing a nice swap to go along with your freshly busted cases, keep reading as this article is for you, and it will hook you up with what you need to know, as well as the parts you'll need, and that are related to laying the power down.
This page is divided into sections for you which you'll find shortcuts to above, in each section you'll find specific recommendations on component replacement, as there are many components besides the chain and sprockets that are at work in this operation.
Beginning at the front sprocket (often referred to as the "Countershaft Sprocket") and moving towards the rear wheel, you have a chain, a chain slider on the swingarm, chain rollers above and below the swingarm pivot area, a rear chain slider / guide, and the rear sprocket, all of which are going to be discussed below.
A well lubricated and adjusted set of chain and sprockets is incredibly simple, and is also an extremely efficient way of transferring power to the rear wheel, although a chain that is not aligned properly, or a chain that is dry and lacking lubrication, as well as chain and sprockets that are caked with mud, or other debris, such as having vines wrapped in them can create a noticeable amount of friction and drag in the drive line, resulting in a noticeable decrease in power, so much so that you may feel a loss of power in the seat of your pants, so be sure to keep your chain and sprockets lubricated and properly adjusted, as well as ensuring the drive train remains clean of build up for the most efficient power output, as this will greater enable you to pull the competition on the straights, have a better handling bike, and other parts on the motorcycle may even last a little longer.
Additionally, It's important to remember the forces that are placed on the chain when riding, such as when powering away from a corner, landing from a jump, or when launching across a creek, log(s), or other irregularity on the ground, as well as you can imagine the force being transferred through the chain when powering up a difficult climb.
Before getting too far ahead of everyone, remember that after cleaning the motorcycle, or after each ride, it's a good idea to visually inspect the drive train to ensure the chain and sprockets aren't showing excessive wear.
Some good indicators of whether the chain and sprockets, or other related components on the motorcycle at hand are worn out, or need replacement are:
If you're replacing your chain and sprockets, you may want to review the "Final Drive Ratio" chart to the right, as this will provide the gear ratios of common sprocket combinations.
Note: When replacing the chain, or either front or rear sprocket, be sure to replace all 3 pieces as a Matched Set, otherwise wear of any new parts will be greatly accelerated.
Simply put, just replace the chain and both sprockets as a set, and do not only replace the rear sprocket while using an old chain and countershaft sprocket, nor any other combination of mismatched parts.
There are several Chain and Sprocket Combo's available, so be sure to review the choices available for your bike, then pick a chain and sprocket combination with the gearing that you feel is best for your intended use.
If the front (countershaft) sprocket is secured with a bolt, bolts or a nut, It's best if you loosen any threaded retaining device with the chain installed, as doing so will prevent the sprocket from turning. Since the chain and sprockets will still be a complete set, the countershaft sprocket can be held from turning by application of the rear brake.
When removing any retaining bolt(s) or a nut from a countershaft sprocket, it is okay to use an impact wrench to remove the securing bolt(s) or nut, although after the chain and sprockets have been installed as a set, be sure to use a torque wrench during reassembly to tighten the bolt(s) or nut securing the countershaft sprocket as can be ccomplished by holding the rear brake to prevent the sprocket from turning during torquing.
If your dirt bike has a washer with a tab that is bent over, securing the nut on the countershaft sprocket, be sure to replace this lock washer with an OEM Replacement upon removal, as these are designed to be used only once, and they get looking hammered if re-used. If the sprocket is retained with a snap ring or circlip, it's a good idea to also replace the snap ring / circlip after removal, but the snap ring / circlip can be reused if necessary as long as it is removed and reinstalled carefully so as to not expand it too far during removal or installation.
If the countershaft sprocket is held in place with a snap ring / circlip, it's a good idea to apply some "yamabond" or another similar type of sealant to the snap ring once installed and securely in the groove, as doing so will provide added assurance against the snap ring coming off.
The front chain slider is a common wear item that is designed to keep the chain from sawing through the swingarm. So... If your chain slider is worn, then replacement is important so as to keep your swingarm intact and not losing weight from the chain sawing through it.
There are aftermarket chain sliders available separately, and in kits which are more durable than the OEM unit and also come in different colors, so these are an option to consider when replacing the front chain slider.
Additionally, you may find that replacement of the swingarm chain slider may be possible without removing the swingarm but if the front chain slider is in need of replacement, this is a good time to remove the swingarm, as well as the shock linkage (if applicable) from the dirt bike and service the swingarm and linkage bearings in these components, finishing the job by fitting the chain slider to the swingarm, then reinstalling the swingarm (and linkage if applicable and removed) to the dirt bike, and reassembling everything that may have been removed, as well as ensuring the chain is adjusted properly, as this will ensure that the chain and sprockets remain in proper alignment.
Keeping the motorcycle's chain roller(s) fresh and rolling smoothly will help keep everything working smoothly, so pay attention to the chain rollers when prepping the bike for a ride or a race. If the rollers are worn, or the bearings inside the roller (if bearing equipped) are feeling rough, or if there is play in these bearings, the chain roller(s) should be replaced.
The upper chain roller keeps the chain inline during hard landings or bottoming of the suspension, as well as keeping the chain from gnawing through the air intake boot, or subframe during travel of the rear wheel, so both the upper and lower chain rollers are important to keep an eye on and TM Designs manufactures a very durable chain roller that you may want to consider.
Remember... The bottom roller takes quite a bit of punishment from the chain so pay close attention to it, as well as the top roller, as the top roller is designed to limit the chain's movement when landing from jumps, or any other condition that causes the rear wheel to blow through the travel.
Moving towards the rear you're going to find a chain guide / slider and this is usually held to the swingarm by through bolts. In OEM applications, the rear chain guide is normally made of an outer shell, with an inner insert that is designed to withstand the chain being in constant contact, as well as keeping the chain feeding onto the rear sprocket preventing derailment.
Most rear chain guides are 2 pieces, and the outer shell that holds the slide block is usually aluminium in OEM applications, or it may have been upgraded to carbon fiber for the "Bling" factor, but the problem with these is that aluminium bends and stays bent if struck, and carbon fiber breaks, both of which scenarios can cause problems with the efficiency of your chain and sprockets. Fortunately, TM Designs has developed a rear chain guide that is nearly indestructible and if you are going to be replacing the wear insert inside the OEM chain guide shell, it is highly recommended that you upgrade to a TM Designs chain guide and rub block.
The rear sprocket is where the power meets the wheel and is usually also the first component of the drive train to show noticeable wear and this is especially true with an aluminium rear sprocket.
Luckily, the people at Renthal have taken notice of this and have developed a "Twin-Ring" sprocket that is designed to address this issue as this hybrid sprocket has an aluminium center to save weight with an outer steel ring that provides greater wear characteristics, so this is an excellent choice when replacing the chain and sprockets as a set, and the "Twin-Ring" sprocket can usually be added to any chain and sprockets "kit" while selecting preferences such as gear ratios, colors and the like.
When replacing the rear sprocket, be sure to use the proper size Allen tool to loosen the bolts if threaded into the rear hub. If the dirt bike has a bolt and nut configuration, be sure to loosen the nut from the back of the sprocket while holding the Allen bolt from turning with the proper size Allen wrench from the front, otherwise damage to the bolt may occur.
If the bolts, or nuts and bolts that secure the rear sprocket have seen better days, you may want to pick up a sprocket bolt kit so as to enable a clean & professional installation of the rear sprocket.
While the rear wheel is removed from the dirt bike for replacement of the rear sprocket, it's also advisable to check the condition of the rear wheel bearings by turning them with your finger. If the wheel bearings feel notchy or rough, NOW is a good time to replace these.
When reinstalling the rear sprocket to the hub, be sure the area where the sprocket attaches to the hub is clean and free of any burs or other imperfections, then tighten all the bolts evenly, and in a criss-cross manner. On the type with threaded holes in the hub with no nut at the rear of the sprocket, make sure you clean the bolt holes in the hub and the bolts with a cleaner such as "brake clean" then apply blue Loctite (both available at local auto parts stores) to the threads of the bolts before installation and tightening.
Once you're done with the rear wheel, the sprocket is installed, and the wheel bearings feel alright, or you've replaced them, before you reinstall the rear wheel, be sure to remove the chain adjuster bolts from the swingarm (if equipped) and coat these with an "Anti-seize" compound so as to prevent the bolts from seizing in the aluminium, making future chain adjustments very difficult, or impossible, requiring future work on the swingarm to correct the situation.
When replacing the chain and sprockets, you'll likely find that the new chain is much longer than the chain that you just removed, but before you do anything keep reading.
Once everything is back together on the motorcycle, It's a good idea to put some thought into where you want the rear wheel to be positioned in the swingarm, then position the wheel there as a starting point.
Remember, The rear wheel position can affect handling characteristics in a noticeable way, such as increasing straight line high speed stability, and decreasing the likeliness of wheelying by moving the rear wheel towards the rear of the adjustment range. Similarly, a bike can be made to turn sharper, and be more responsive to throttle input by shortening the wheel base (moving the rear wheel forward), so rear wheel position is something that some thought should be given to before wrapping the chain around the sprockets and determining the length.
Once the wheel position is determined, wrap the chain around the sprockets (with the wheel set in position and the axle nut snug). Over lapping the ends of the chain you should be able to determine where you need to break the chain.
Once you know where to break the chain, grind the peening off the end of the pin(s) that are to be removed, then use a quality chain breaker to break the chain, or drive the link out using a hammer and punch supporting the chain over a vise with the vise jaws open just enough to allow the link being removed to be forced out.
Once the chain and sprockets are installed and the chain is wrapped around the sprockets, be sure to position the master link so the clip is towards the outside of the chain (facing you) while also insuring the orings (whether oring or xring style) are in place properly during assembly of the masterlink to the chain.
When you're cleaning the dirt bike and addressing the chain and sprockets it's best to spray the chain with the cleaner of your choice from a hand held pump sprayer (Simple Green works well, See Washing a Dirt Bike) while turning the rear wheel, then once soaked with a cleaner, using a common household type of stiff bristle nylon brush, or a chain cleaning brush, scrub the chain including the side plates, and the top and bottom of the links, as well as trying to get to the teeth on the sprockets while you're at it. (cleaning of the sprockets may be easier with "Scotch-brite").
Once the drive train is soaked well with cleaner and has been scrubbed, it is important to rinse everything well and if you have a non-oring chain, it is alright to use a power washer, but on a sealed chain such as an oring chain or any other variation of a sealed chain such as an xring, you may want to keep a pressure washer away and just use a moderate pressure, such as from a garden hose to rinse the chain so as to not disturb or dislodge any of the seals within the chain, or to force grit particles deep within the chain rollers where they will not be able to escape and will cause accelerated wear of the drive chain.
Once the drive train is clean, and you have also finished with the cleaning of the rest of the dirt bike and you've shut the water off, you need to use compressed air to dry the chain and sprockets as well as other related and non-related components on the dirt bike as shown in the article on washing a dirt bike.
Once you have begun to dry and displace the water from components as mentioned in the article on washing a dirt bike, it's time to focus on the chain.
Using compressed air with a blow nozzle, slowly turn the rear wheel by hand while at the same time using the compressed air to dry the chain and displace water from between the side plates and rollers as well as from the sprockets and general areas.
Once the motorcycle is clean and dry, it's important to lubricate the chain with a quality chain specific lubricant applied to the chain just above the bottom roller, on the sprocket contact side, NOT on the top of the chain as it passes by on the top of the swingarm.
Once the chain is lubricated, be sure to review the section on chain adjustment below to ensure the chain is properly adjusted and rear wheel remains in proper alignment.
Ensuring the proper amount of slack remains in the chain, so as to permit unrestricted travel of the rear wheel over irregular terrain, or when landing from a jump is critical to the life of bearings and other components, so this should be done with the utmost care.
Having the chain free-play set properly, as well as having the chain and sprockets aligned properly will enable you to extract the maximum amount of performance from your bike, as well as avoiding any derailment problems and accelerated wear of components.
Once everything is clean, grab a small ruler (A 6" machinist steel rule works well) and find a point on the chain to reference from that is slightly behind where the front chain slider ends.
A good point on the chain for this is usually one of the pins in the chain, as these are centered within the chain and are an excellent reference point.
Forget all the stuff you've heard about taking a measurement when the swingarm is parallel to the ground, or at full travel. Taking a measurement with the swingarm at these points is usually very difficult and a hassle to say the least. Ideally, you'll want to take a measurement with the chain at rest on the slider while the dirt bike is on a stand with the rear wheel off the ground and hanging with the rear shock(s) fully extended.
Once you've a spot on the ruler visualized with the rear wheel at rest, position the ruler next to the chain while lifting the chain with your other hand until taut, then take another measurement.
The ideal free-play setting for a chain is about 1.4 - 1.5 inches from the first measurement while everything is at rest as discussed above. If the free-play is adjusted to where there is 1.4 - 1.5 inches of slack in the chain, there will be sufficient free-play to allow the swingarm full travel without pulling the chain so tight that things are in a bind resulting in possible breakage of the chain, which usually results in broken engine cases, and is very expensive to repair. Additionally, keeping the chain in proper adjustment will help avoid prematurely worn swingarm and engine bearings due to the load placed on these components from a chain which is too tight. Finally, a chain which is excessively loose will create problems due to "chain slap" so maintaining the proper chain tension is an important adjustment and setting at both ranges.If your chain needs adjustment such as when installing a new chain and sprockets, or when compensating for wear of drive train components the following tips will ensure a trouble free adjustment.
When adjusting the chain (taking out slack), a tip that works well is to loosen the rear axle nut while still leaving a moderate amount of torque on the nut so the rear wheel cannot be slid in the adjusters by hand. Then use the adjusting bolts (or other means of adjustment as provided by the manufacturer of your bike) to push the wheel back evenly on each side making sure the alignment marks remain equal on either side before tightening of the axle nut further, or to the factory recommended torque value as can be found in a factory service manual specific to the motorcycle.
Once the axle nut is tightened to the factory recommended torque value, apply light pressure against the axle blocks by holding the chain adjuster bolt (if equipped) with one wrench, then firmly tighten the chain adjuster lock nut while using another open ended wrench simultaneously, repeating the process for the other side.
The proper free-play of the chain is very important and fairly easy to set, but maintaining proper alignment is equally important, and the marks on the factory adjuster are not always the best, nor are they often accurate due to tolerances in the manufacturing of the frame and swingarm, so you may want to consider aftermarket axle blocks in the color of your choice to aid in alignment of the rear axle and add a little bling to the rear of your swingarm, as well as picking up a chain alignment gauge to ensure proper alignment of the chain.
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