Chain Drive Replacement, Modification & Maintenance
by Mark Barnes, Ph.D.
motorcycles can go thousands of miles
between thoughts about their
final drives, but owners of chaindrive bikes must be more conscientious if they want to
avoid being stranded—or
worse—by component
failure. In this article,
we’ll cover chain and
sprocket care, from complete
system replacement to routine
adjustment and lubrication. Our
latest test mule, a 2000 Suzuki
SV650, will serve for illustration,
but the same principles and procedures apply to the vast majority of
chain-drive machines. Consult your shop
manual for details specific to your bike.
When to Start Over
Generally, chains and sprockets should
be replaced together. Running a worn chain
on new sprockets, or vice versa, will cause
accelerated wear to the new part(s). However, parts without visible wear may be
safely retained when swapping others, for
instance, during gearing changes.
Chain “stretch” is really a misnomer, as
no part of the chain is truly stretched. A
worn chain does become elongated, but the
cause is actually wear on the chain pins and
bushings. Ever larger clearances allow the
links to spread further apart; thus, the
chain’s length grows.
Your shop manual will call for a certain
number of links to be measured with a
caliper to determine wear, and the service
limit is typically 2–3% longer than brandnew. But even without formal measurement, a chain’s wear can be visually
assessed by attempting to pull it away from
the back side of the rear sprocket. Fresh
parts won’t allow any movement, but manufacturers will usually call for replacement
when between a third to a half tooth is
exposed by this method.
Corrosion and other factors can also lead
to localized binding. Our SV arrived with
its original chain in dreadful condition after
20,000 miles and 12 years. Probably due
to inconsistent lubrication, it had some
extremely stiff joints. When the bike
moved at low speeds, this chain made a
rhythmic “shhh-shhh-shhh” sound, similar
to a warped rotor rubbing against brake
pads (the lack of pulsing at the brake lever
clarified the diagnosis).
Sprocket wear is easy to spot. Teeth typ26
A motorcycle’s entire final drive system can be contained in these three
small packages—if that motorcycle
uses a chain.
ically become thinner, sharper and finally
“hooked” as they lose their tight interlocking fit with the chain, which gradually rides
ever higher—putting more strain on less
tooth material under acceleration loads.
The resulting shark-fin shape is clear evidence of the need for replacement. Teeth
can also chip as a result of debris being
caught between the chain and sprocket.
Another type of wear occurs from
sprocket misalignment, either because the
rear axle is cocked due to improper adjustment, or because the swingarm is bent or
worn swingarm bushings and/or wheel
bearings haven’t kept the rear axle perpendicular to the chain. Sprockets that show
asymmetrical wear between the inboard
and outboard sides of their teeth can be evidence of this condition.
Tools Of The Trade
Before launching into a full-scale final
drive replacement, you’ll need to collect
a few things. Obviously the new chain and
sprockets must be chosen, but you’ll also
need a multi-purpose chain tool. These are
used to a) “break” endless chain (an OEM
or replacement chain that lacks a clip-type
master link), b) remove links from a new
chain that’s longer than necessary, and c)
install a rivet-type master link (the most
common type on street bikes). These tools
are available in different sizes and configurations and across a wide range of prices.
We like Motion Pro’s chain tools, and
have used their “Jumbo” model ($139.99
MSRP, but available for less online) for
years with complete satisfaction. However,
Motion Pro’s $84.99 PBR model also
seems an excellent choice,
although we haven’t tested
one yet. It has clever markings on it to remind its user
how to properly configure
it for pressing, breaking
and riveting chain links.
Keep in mind that a tool simply called a “chain-breaker” can
usually only perform that one function. (See www.motionpro.com)
Drive sprocket replacement will
require a heavy-duty torque wrench (our
SV’s countershaft sprocket retaining nut
needed 105 lb.-ft. of torque), appropriately
sized sockets (32mm on the SV), and a
breaker bar or impact wrench. Of course,
it’s a good idea to use a torque wrench to
properly tighten your rear axle nut, wheel
sprocket retaining bolts and the rear brake
torque-arm fasteners any time you remove
the rear wheel or adjust chain slack. Other
useful items include a sprocket alignment
tool, an easy-to-read ruler (metric makes
subtracting numbers easier), and a dial or
digital caliper for measuring pin flare on a
rivet-type master link. You may also need
OEM parts, such as a fresh lock washer for
the countershaft sprocket retaining nut.
Break It Down
Strip off everything in your way, like the
chain guard, countershaft sprocket cover,
and—if your bike is so designed—clutch
actuation hardware. Read the related sections of your shop manual before taking
things apart for any special procedures.
A worn-out endless chain will come off
whole if you remove the swingarm, but it’s
much easier just to break the chain. This
can be done with a hand grinder and a small
punch, using the former to grind off the
staked end of a chain pin and the latter to
force that pin out of its bushing. But it’s
much easier to use a chain tool, which
clamps onto a link and forces its pin out
using a powerful screw mechanism. But as
the chain pin is made of hardened steel, it’s
still not a bad idea to grind off the head of
the rivet first, to eliminate the possibility of
breaking the tool’s pushing bit.
If the old chain has a clip-type master
link, the job may be as simple as slipping
off the master link’s clip, removing the
Our SV650 had a terribly neglected
chain. Everything under the sprocket
cover was coated in sticky, gooey grime.
Motion Pro’s Jumbo Chain Tool set for
breaking. The smaller post forces the pin
through the link to separate the chain.
Chain tool in position over the pin to be
forced out. Box-end wrench is tightening
the threaded shaft against the target link.
sideplate, and sliding it out the other side.
But some of these clipped links are so
tightly pressed into place that they require
the same treatment as an endless chain.
With a pin or master link gone, the chain
can be pulled off the bike easily. However,
it may be able to serve a final purpose
before being removed and discarded.
Countershaft sprocket retaining nut
removal requires that the countershaft be
held still. Putting the transmission into a
high gear may work, but the high torque
necessary to break it loose may also put a
strain on your gearbox. Leaving the old
chain in place makes possible an alternative. You can apply the rear brake, so that
with the chain in place, this immobilizes
the countershaft.
Many countershaft sprockets use a special locking washer to prevent loosening of
the retaining nut. These are wide, splined
rings made of metal soft enough to allow a
section to be bent against a flat on the retaining nut. These must naturally be re-flattened
before removing the nut. This can be
accomplished with a hammer and a chisel or
thin flat-blade screwdriver (their tips may
chip in the process, so wear eye protection).
A 1/2"-drive air impact wrench or similarly
powerful electric impact tool can then
quickly spin off the retaining nut. Without
one, a large breaker bar will be needed, as
these nuts are very tight. See your shop
manual for the correct procedure if your
bike uses a different retention system.
Note that countershaft sprockets aren’t
always symmetrical front-to-back, so be
sure to have the proper face outward when
mounting the replacement. You may have
to wait until the new chain is installed (to
again immobilize the countershaft) before
torquing the retaining nut. Afterward, the
edge of the lock washer can be lifted and
then pressed squarely against a flat on the
retaining nut with a large pair of slip-joint
To change the rear sprocket, remove
your rear wheel and lay it sprocket-side up
on a wheel stand, wooden blocks, or extra
tire. Make sure your brake rotor doesn’t
bear any weight as it can easily be bent out
of true. Sprocket retaining nuts are usually
on very tightly, and it can be difficult to
keep the wheel from rotating as you try to
undo them. This would be another good
occasion for an air impact wrench. Other-
wise, pull your breaker bar or long-handled wrench in an arc across the wheel’s
center. This will put you in the best position to hold the wheel still while maximizing your leverage on the nuts.
Once freed, the bolts that held the
sprocket will probably fall into the wheel
hub. Pull the hub out of its rubber dampers
and notice their orientation, so you can
reposition them correctly during reinstallation. Inspect the sprocket carrier’s wheel
bearing, and apply fresh grease if needed.
Reverse the process to install the replacement rear sprocket using proper torque on
the nuts, and the rear wheel can now go
back on. Set the axle adjusters to their most
forward positions without tightening anything to ease the job of getting the new
chain over the rear sprocket.
Thread the chain around the front
sprocket and bring its ends together at two
o’clock on the rear sprocket; this keeps the
end links aligned and lets you insert the
master link without having to also support
the ends of the chain. The ideal length chain
(with proper slack) will situate the rear
wheel in the forward third of its adjustment
Pin halfway out. We paused midway
through the operation to show what’s
normally hidden by the chain tool.
Once broken, a chain is easy to remove.
Otherwise, the whole swingarm would
have had to come off to free it.
Look closely and you’ll see the near edge
of the lock washer has been bent against
one flat of the countershaft sprocket nut.
Turn, Turn, Turn
Together Again
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Wear eye protection when using a screwdriver and hammer to pry the lock washer’s tab away from the retaining nut.
The flattened lock washer’s beaten down
side is weakened. If you reuse it, use the
opposite side for the new locking tab.
Removing the countershaft retaining nut
requires locking the rear wheel and
using a breaker bar or an impact wrench.
range, leaving plenty of room to take up
excess slack as it wears.
Always use the same brand, size and
type master link as your chain; new chains
will have one included. Coat O-rings (if
present) liberally with high-pressure
grease (also usually included) and slip
them on the pins. Cover the pins with
grease and fill the holes where those pins
will go. Insert the pins into the chain ends
from the inboard side, then slip the remaining O-rings, also greased, onto the pin tips.
Depending on the master link’s tolerances, pressing the outboard sideplate onto
its pins may require considerable force,
and the sideplate must be pressed on
evenly. This is best done with a chain tool
(reconfigured now to press mode), but slipjoint pliers may also work if their handles
afford adequate leverage. The sideplate
must go on far enough to allow adequate
securing by the clip or pin flares, but not so
far that it causes binding with adjacent
links. This takes patience. Carefully monitor the master link width while you
squeeze, and stop when it’s almost even
with its neighbors. You can always apply
more pressure if needed, but it’s virtually
impossible to reverse the process.
On a clip-type master link, the sideplate is
on far enough when the grooves in the pins
have been fully exposed to allow the clip to
seat properly. Always mount retaining clips
with the closed end pointing in the direction
of movement (i.e., toward the front of the
bike when on the top chain rung). Mounting
these clips can be tricky because of their
high tension. They tend to either fly off or
end up stuck in a not-quite-seated position,
quickly losing the ability to return to their
original shape, rendering them worthlessly
loose when finally in place. Apply pressure
exactly in-line with the two master link pins,
and be sure those grooves are fully exposed.
If you lose or deform the clip, you’ll have to
purchase a whole new master link, as new
clips aren’t sold separately. For additional
security, clips can be safety wired after
mounting (fold the twisted wire back toward
the clip’s open end).
Rivet-style master links require the use
of a chain tool to flare their pin tips. In this
process (with the chain tool in rivet mode),
a tiny dome-shaped anvil is centered over,
and then pressed against, each pin’s “dimple” (the hollow in its tip). The resulting
flared pin prevents outward movement of
the sideplate. Again, it’s critically impor-
tant to apply enough force, but not too
much. Inadequate flaring may leave the
sideplate unsecured, while excessive flaring will bind the master link or crack the
pin, necessitating master link replacement.
Get the pin flare spec from your chain’s
manufacturer, available either in the packaging or on their website. Use a dial or digital caliper to measure flare width along the
way. Remember, you can always create
more if it’s not yet flared to spec, but you
can’t go backward.
Your new setup is now ready for slack
The old sprocket (right) is slightly
“hooked.” Its replacement is lighter, and
lacks the noise-dampers of the stocker.
Cleaning the grungy chain pathway was
by far the worst part of the entire job,
but once clean, it looked much better.
Wheel Removal—Rear wheel liberation
is very simple once the chain is out of
the way.
Check It Out
Excessive chain slack will result in driveline snatch, and can, in extreme cases,
allow the chain to jump a tooth or completely fly off a sprocket during operation.
Inadequate chain slack can break the output
shaft, as well as put additional strain on the
chain, possibly resulting in its failure.
Either way, the consequences can be catastrophic. Slack adjustment is a simple,
albeit tedious, procedure that should be
checked regularly.
Chain slack is affected by the drive
sprocket’s concentricity and not all drive
Now is a good time to check the wheel
bearing inside the hub. Ours was in fine
condition, but a bit low on grease.
A fresh slathering of wheel bearing
grease now, when it’s convenient, may
prevent inconvenient problems later.
Pull the breaker bar in an arc across the
wheel’s center to put more force on the
nut and less on the wheel.
sprockets are perfect. Inconsistent flexibility along a chain’s length can also make
significant differences in how much slack
shows up, depending on which links are
being checked. Turn the rear wheel to find
the point of least slack and set the recommended chain slack at this point. Also, be
sure to have your bike supported properly
for the measurement. If your manual gives
you a slack spec for the bike on its sidestand, don’t take the measurement with the
bike on its centerstand. If you don’t have a
recommended slack figure, remember that
when the centers of both sprockets are
aligned with the swingarm pivot (which
may take some heavy weight on the rear
suspension with the wheels on the ground
to achieve), the chain will have minimum
slack and it should still have some noticeable slack at this point.
To measure slack, locate the middle of
the lower run of the chain, and with a ruler
stabilized against the swingarm, push down
lightly on the chain and read where its
upper edge rests against the ruler. Next,
push the chain upward with the same pressure and take a second reading at the exact
same place on the chain. Subtract the second measurement from the first; this is your
slack. It’s best to be toward the looser end
of the acceptable range; this may mean
more frequent adjustments, but it guards
against the possibility of engine and/or
chain damage caused by inadequate slack.
Those hash marks on your swingarm can
help get your adjusters “in the ballpark,”
but they’re notoriously imprecise and can’t
be relied upon for accurate rear wheel
alignment. Proper alignment will ensure:
a) the rear wheel is in-line with the front
wheel, b) the rear wheel is parallel with the
swingarm pivot, and c) the rear sprocket is
in-line with the countershaft sprocket.
Ideally, these would all be synonymous,
but inconsistent manufacturing tolerances,
especially in the manufacturing of frames
and swingarms, can create misalignments.
Various alignments can be given priority, depending on an owner’s preference.
Wheel alignment may be more important to
some, as it affects handling, than perfect
chain alignment, and there are a variety of
tools available to make a variety of measurements. Keeping the swingarm pivot
parallel to the rear axle is sensible, and
Muzzys Performance Products makes a
special tool for this job. It has cones that
can be arranged on a graduated bar to
ensure the distance from pivot to axle is the
same on each side (www.muzzys.com);
If sprocket alignment is your priority,
you can use Motion Pro’s Sprocket Alignment Tool, which clamps onto the rear
sprocket and allows sighting down a
pointer that mimics the sprocket’s plane (a
straightedge against the rear sprocket might
also work, if space allows).
Once you are satisfied, torque all the
related fasteners and check slack again, as
the tightening process can sometimes cause
it to change, either due to accidental
adjuster movement or because of design or
manufacturing anomalies. Re-adjust until
it’s just right.
Nobody wants to repeat tedious work
more than necessary. Once the rear is
aligned, slack adjustments will be quick if
you very carefully turn each adjusting bolt
just one flat at a time—moving them both
the exact same distance. Check slack again
after the first 100 miles as chains typically
wear most rapidly when new (assuming
they aren’t neglected or abused later), and
inspect alignment regularly.
Our SV’s driven sprocket (left) wasn’t
terrible (new on right) but its wear was
no doubt accelerated by the worn chain.
Greasing a new master link: The O-rings
and the bushings will all be thoroughly
coated. This is the clip-type master link.
It was barely possible to squeeze our
clip-type master link’s sideplate on with
long-handled, parallel-jaw pliers.
Let’s Get Something Straight
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Master link clip installation requires the
pin grooves to be fully exposed. We’re
using a pair of needle-nose pliers.
For security, we safety-wire master-link
clips on dirt bikes. The clip’s closed end
points in the direction of chain travel.
Chain tool in press mode: You may be
surprised at how much force is required
to press fit the sideplate onto its pins.
Final Touches
wheel a few extra revolutions to work in
the lube. Ideally, chains should be lubed at
operating temperature; at the end of a ride,
not the start, and the lube allowed to set-up
(giving time for the lube’s thinning solvents to evaporate) before riding again.
We’re not sure expensive chain lubes do
much more than plain old WD-40 or silicon-based lubricants when it comes to Oring chain maintenance, athough they must
be applied more often. Use a dedicated
chain lube if you’ll be riding through dust
or rain. For less extreme conditions,
cheaper general-purpose products may
serve just fine, and sling less mess onto
your rear wheel.
The white grease on your new chain
should be wiped off before use; it’ll
quickly fling off the chain and what
remains will catch and hold debris. Use a
chain-specific cleaner or WD-40. Subsequent cleanings may require brushing to
remove grunge from the chain’s myriad
cracks and crevices, and the aptly named
“Grunge Brush” works well (see Innovation of the Month, January 2011). Never
use a wire brush on O-ring chains, as it can
damage the O-rings.
Lubing a chain is something best done
while spinning the rear wheel by hand with
the bike on its centerstand or supported by
a work stand. Aim the spray can’s straw
downward onto the sideplates, both inboard
and outboard, on the lower rung. Spin the
If your bike’s final drive ratio doesn’t
suit you, it’s easily changed. If you’re
already replacing worn components,
there’s little additional cost involved. For
easier take-off from a stop and more vigorous acceleration, choose “shorter” gearing—that is, gearing with a higher
reduction ratio. For instance, a 15-tooth
countershaft sprocket paired with a 45tooth rear yields a final drive ratio of 3.00:1
(45/15), meaning the front sprocket turns
three times for every revolution of the rear.
Switching to a larger rear and/or smaller
front will give the engine greater leverage—just like shifting to a lower gear.
Pairing a 14-tooth front with that 45tooth rear will yield a final drive ratio of
3.21:1 (higher ratio = “shorter” gearing).
Or, you could go up three (to 48) out back
for the same result (48/15 = 3.20).
Although front sprockets are typically
cheaper than rears and don’t usually
require a new, longer chain, there are reasons for going with the bigger rear
sprocket: One is pressure on the chain
slider (the plastic piece that prevents the
chain from touching the top of the
swingarm). Smaller countershaft sprockets will also increase the “squat” effect
inherent in chain-drive systems during
acceleration and cause the slider to wear
faster. Smaller drive sprockets also
increase friction and accelerate wear as
each link in the chain must bend more
tightly around the sprocket’s smaller diameter on every revolution.
Rear sprocket size increases may, however, be limited by other factors, such as
chain guard height. Before selecting your
new sprockets, check such clearances.
Shorter gearing delivers harder acceleration in each gear, but each gear will also
have a lower top speed. Likewise, at any
given road speed in a particular gear, the
engine will be spinning faster, and gas
mileage will drop accordingly. So, riders
seeking a higher top speed, improved
mpg, increased range, or simply a more
relaxed engine while cruising rpm may
want taller gearing—if they can live with
Chain tool in rivet mode: A tiny domed
anvil is centered over each pin’s dimple
and pressed to secure the sideplate.
Pin Flare: The lower pin has been
correctly flared by the chain tool; the
upper one’s dimple is as-yet untouched.
Getting the flare just right requires a
caliper. It needs a lot of force to create,
but a tad more could crack the pin.
Making Gearing Changes
With the new chain installed and the
retaining nut retorqued, a side of the
lock washer must next be pried up…
Press Fitting Locking Washer Tab:…and
using an undamaged side of the washer,
pressed flat against the retaining nut.
Checking Slack: Tug down to get the first
measurement, push up to get the second; the difference is your chain’s slack.
softer acceleration. It’s always a trade-off!
Check www.gearingcommander.com for
ratio tables.
If your bike’s speedometer uses a countershaft speed sensor rather than a front
wheel speed sensor or worm-drive speedo
cable, changing sprocket sizes will distort
its readout (and the odometer’s). A recalibration module like the SpeedoHealer
(www.healtech-electronics.com) will also
be needed or you’ll have to mentally adjust
your speedo reading by the percentage of
final drive ratio change.
Changing sprocket tooth count may
change the required chain length. Add one
link for every tooth added to your sprockets. But, whether or not you change your
sprockets’ number of teeth, you may want
to change their size, along with that of
your chain. Why?
centers) in eighths of an inch. Most motorcycle chains begin with “5,” and thus have
a 5/8" pitch; “6” is for 6/8" or 3/4". The
remaining numbers designate the width
between the inner sideplates. Chains ending in 20 have 2/8" or 1/4" clearance,
those ending in 25 (read 2.5) have 5/16"
clearance, and those ending in 30 leave a
3/8" space. Chain and sprockets must be
the same size.
Switching to a 520 chain can result in
reduced friction and more than a pound of
weight savings. But you should check the
maximum engine size/horsepower recommended for any chain under consideration.
Also, since racers are the most interested in
saving weight, and have the greatest need
for the widest variety of gearing options,
the largest selection of chains and sprockets to choose from are in the 520 size.
Variations on this theme are seen in XRand XW-ring chains. Non-O-ring chains
don’t have any seals, therefore wear more
quickly and are consequently rare.
Chains vary widely in price; don’t
spend more than necessary. High-end
chains may provide “advantages” that are
meaningless in normal use, such as miniscule additional weight savings, colors or
strength that’s just more overkill on noncompetition machinery. Buy the least
expensive X-ring chain you can find for
your engine size/horsepower from a reputable manufacturer (e.g. D.I.D., EK, RK,
Regina or Renthal). Don’t cheap out with
questionable hardware! Having a chain
break could result in not only the loss of
forward thrust, but also sudden rear wheel
lock-up and/or severe engine damage—
not to mention leaving you stranded or
possibly with a physical injury.
Chain Sizes
Chain Types & Prices
Changes in size differ from changes in
length. The most popular is the “520 conversion”—replacing a stock 525 or 530
chain with a smaller, lighter 520 aftermarket chain. Chain numbers specify two
dimensions: The first digit indicates a
chain’s pitch (the distance between its pin
O-ring chains have—as you’d guess—
tiny O-rings that seal grease in their bushings. X-ring chains simply use seals with an
X-shaped cross-section. This shape traps
additional lubricant along each seal-sideplate interface, increasing the chain’s
flexibility and further decreasing wear.
While this article may inspire you to purchase the special tools you need to break
and rivet chains and change sprockets, it
should also make you appreciate the skills
you’ll have to pay for if you let someone
else do the job. Happy wrenching!
To get a more precise measurement of
axle position, we’ve used the much finer
increments on our machinist’s ruler.
Motion Pro’s Sprocket Alignment Tool
clamps to the rear sprocket and should
point straight to the countershaft sprocket.
Lubing: Aim downward at the sideplate
junctures when lubing your chain, and
do both the inboard and outboard sides.
Bottom Line
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