Chain Monkey Review
A Motorcycle Chain Tension Measuring Tool
wBW Quick Look
by "Mad Dog" Earle for webBikeWorld.com
Owner Comments (Below)
Motorcycle Maintenance & Repair Articles
Motorcycle Chain Lube Reviews
Tips on Adjusting a Motorcycle Chain
The Chain Monkey is a tool to help set the correct motorcycle chain
slack during a chain adjustment.
It's made from plastic with an adjustable metal screw.
Follow the instructions in the kit and set the bottom of the nut to
your correct optimal chain slack number.
Then tighten the rubber stopper on the bottom.
Unscrew the threaded rod, place the Chain Monkey over your chain and
tighten until the rubber stopper meets the plastic.
This puts a kink in the chain.
Then adjust the chain by using the nuts on the swingarm. Adjust until
the chain is very tight, then tighten the swingarm nut(s).
Remove the Chain Monkey and the chain should be within spec.
There are a couple of degrees of freedom here: how closely
the Chain Monkey is set; whether or not the rubber stopper has moved and
how tight to make the chain using the motorcycle's adjustment screws.
But, with some practice, it's not too difficult to get it right the
Also, the black plastic tip that pushes on the chain wears very
quickly. I noticed this right away even after the first use.
So while the Chain Monkey isn't a perfect solution, it does have a
few advantages. The
alternative is using the Ol' Standby method described below: use a millimeter rule to
measure slack, then adjust, then check.
So the Chain Monkey can theoretically eliminate one step in the
Worth it? Probably so, especially if you do a lot of chain adjusting.
Here's a Quick Look in photos:
The Chain Monkey is made from solid plastic with hollow plastic arms.
Measuring chain slack the
traditional way, with a millimeter rule. Hold the rule steady by resting the hand against a tire or other item. Line up a major
index on the bottom of a chain plate (photo left); in this case, the
40 mm mark. Pull up on the chain with the other hand while keeping the rule steady (photo right). Read the number
(13 mm here) and subtract from the first to get the amount of chain
slack. Follow instructions in owner's manual; most bikes should be
on the side stand, not center stand.
Measuring Chain Slack the Old Fashioned Way
"Old Fashioned" means using a rule to measure chain slack, as in the
"Burn" and I covered this in great detail in the article "How
to Adjust a Motorcycle Chain", so be sure to reference that and
please feel free to add any tips that you might have.
Note that it's important to follow the instructions in the motorcycle
owner's manual for positioning the bike and for the correct amount of
Most motorcycle manufacturers recommend placing the bike on its side
stand (also, most motorcycles don't come with a center stand).
Usually, it's recommended to measure at the tightest part of the
chain, which means you have to rotate the wheel around and measure
several times to find the tight spot.
Since I'm a lazy son-of-a-gun, I never do this. They give you enough
variance anyway in the amount of slack, so you should be fine by hitting
it somewhere in the middle of the range.
A common chain slack measurement is 25-35 mm, for example.
In the old school method,
you hold a millimeter rule and place one of the easy to remember (and
easy to subtract from) index points at the bottom (or top or center) of
the slack chain.
Pull up on the chain while holding the rule steady and read the
difference. Subtract from your first reading and you have a rough idea
of the chain slack.
In the photo above, the rule was held so the arbitrary 40 mm mark was
even with the bottom of the chain.
Pull up on the chain without moving
the rule and read the mark aligned with the bottom of the chain again,
then subtract from the first reading.
40 mm minus 13 mm = 27 mm of slack, which is within specifications of
25-35 mm for this bike, the
Versys 650 LT (Blog).
Disadvantages of the Old Fashioned Method
The old fashioned method works fine other than it's a bit clumsy.
- First, having the bike on its side stand can make it difficult
to get down underneath to access the chain.
I've worked on some
bikes where the combination of the way the bike leans over on its
side stand and a big silencer makes it really difficult to get
underneath without putting the bike on a lift.
Double or triple that
anxiety when you have to move the rear wheel around a couple of times
to find a tight spot on the chain or to double- or triple-check your
chain adjustment work.
- Then, there's the matter of moving the rear wheel when the bike
is on the side stand.
You can try something like the
Rollastand rear wheel
roller we reviewed or there are several other
inexpensive wheel rollers you can buy here.
They're not easy to
use and be sure to take a lot of caution when doing so but...they're
better than nothing for moving the rear wheel for a chain adjustment
and/or chain lube.
- And finally, you have to be pretty good at eyeballing the
millimeter scale or rule to find and check the correct amount of
Sometimes it's difficult to hold the rule steady
while you stretch the chain up and down, especially considering
number 1 above.
Close-up of the business end of the Chain Monkey. Note the unused tip on the black plastic or nylon nut cover.
The Chain Monkey can be set for a variety of chain adjustment specifications.
The Chain Monkey fitted on an adjusted chain.
Video: How to Use the Chain Monkey
The Chain Monkey System
The Chain Monkey is made from molded plastic with two "arms" that
hang over the top of the chain made from hollow plastic.
The kit comes with instructions in the package; it's too bad they
didn't include the setting table as a sticker on the back of the Chain
The instructions in the kit are pretty easy to follow.
- First, measure the height of one of the side plates on your
motorcycle's chain. It will probably measure either 10-13 mm for
smaller chains or 14-17 mm for the common 520 chain.
- Next, look on the Chain Monkey chart and match the desired chain
slack for your bike. In our example, the manufacturer recommends
25-35 mm of slack.
- Set the bottom of the nut on the Chain Monkey to the
correct optimal chain slack number found on the chart.
- Move the rubber stopper on the bottom of the Chain Monkey so
that it meets the bottom of the Chain Monkey tool.
- Next, unscrew the threaded rod, place the Chain Monkey over your chain and
tighten until the rubber stopper meets the plastic.
Tightening the screw
via the knob on the bottom pushes the rounded plastic cap into the
chain and puts a kink in the chain.
The instructions are vague on
this, but apparently it's important to place the round black plastic
cover in between two chain links, not underneath a single link.
- Now you can adjust the chain by using the nuts on the swingarm. Adjust until
the chain is very tight, then tighten the swingarm nut(s). This is where
it gets tricky -- how tight is tight enough (see disadvantages
- Tighten the swingarm nuts to the
torque spec, remove the Chain Monkey (don't forget!) and the chain should be within spec.
UPDATE: A webBikeWorld reader pointed out that there is a
small and hard to see instruction on the back of the package that reads:
"Before you begin, remove black plastic cap from domed nut".
I did not see this and all of the photos or video on the Tru-Tension
website show the Chain Monkey being used with the black plastic cap in
It's not clear why they would even put the black plastic cap on the
domed nut if the cap isn't supposed to be used? The instructions should
definitely be more clear about this.
SURPRISE! There's a domed metal nut underneath the black plastic cap. Other than one hard-to-see instruction that I
missed on the back of the package, all of the photos, instructions and videos on the Tru-Tension
website show the Chain Monkey being used WITH the black plastic cap
in place. Apparently, the Chain Monkey can
be used either way.
The single hard-to-see instruction about removing the plastic cap. But note
the instruction photos, which show the cap being used. Fortunately,
either way doesn't seem to make any difference in the performance of
Disadvantages of the Chain Monkey System
- First, you still have the problem identified in
#1 of the Old Fashioned
method above: the bike is on the side stand.
Chain Monkey over the top of the chain can make this even more difficult on some bikes.
- There's also the issue of how closely
the bottom of the nut on the Chain Monkey aligns to your chosen setting
number and being able to see far enough underneath to align the nut with
the correct setting.
- Then, the rubber stopper isn't the best way to set the stop.
you're not watching what you're doing, you can move the bottom of the
nut past your set mark, although admittedly with some practice, it's not too difficult to get it right the
They should have used a metal nut, double nut or better yet, a
Nylock nut that holds position. Fortunately, you can add this yourself.
- Also, the black plastic tip that pushes on the chain
is too soft and it wears very quickly.
the black plastic cap is supposed to be removed, although none of
the Tru-Tension photos or online video show this!
Fortunately, it doesn't really seem to matter whether the cap is
used or not. Perhaps using the cap helps cushion the pressure on the
UPDATE 2: Tru-Tension says "The Chain Monkey can be used
with or without the cap but we have stated to remove it before use
in the instruction as it can then be used to protect the domed nut
- Probably the most significant issue
is the "how tight is tight enough?" problem.
When you tighten the
Chain Monkey to the specified number on the tool, the chain becomes
very tight to begin with when you're even half-way or more to the
limit of slack.
This makes it difficult to know how much more
adjustment is needed on the swingarm adjustment bolts.
chain adjustment can vary at least as much as 5 mm of slack, so it
does take some practice to understand all the variables for your
- It's expensive at a $34.99 list
While the Chain Monkey isn't a perfect solution, it does have a
Once you get the feel of it on your specific motorcycle, you can
usually set the chain
slack in one trip underneath the bike.
There are enough variables that you'll have to practice a few times
to get a feel for how tight to make the chain with the swingarm nuts.
But once you practice, you should be able to hit somewhere in the
correct tolerance every time.
Tips on Adjusting a Motorcycle Chain
wBW Review: Chain Monkey
List Price (2016): $34.99 and up plus S/H
Made In: Unknown
Sizes: Fits various bikes.
Review Date: September 2016
Note: Item provided by a retailer,
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►Your Comments and Feedback
Please send comments to
From "R.T." (October 2016): "After reading your review on the
Chain Monkey -- an answer to a question no one asked.
I see you had it on your Versys, my 2016 like yours clunks bad about
half the time. So after you check the oil and clutch free play and
everything else, like shift linkage (Kawasaki goes into detail about
that in the shop manual).
The drum roll...tighten the chain to 26 mm. It is still in spec and
BINGO! No more clunk.
Seems that the drive train slack was causing it in mine anyway. The
bike came at 30 mm, right in the middle of the spec and clunk.
It didn't go out of spec until 1,200 miles to about 38 mm.
I was going to bring it back to 30 mm but thought it worth a try and
it worked. Now I'm a happy camper, because after 50 bikes I really like
this one and it might be my last full size bike.
I'm 66 and have been riding 52 years, 400 thousand plus miles and
that was the only thing the I didn't like about it."
From "H.F.B." (October 2016): "I thought they ask to remove
the black plastic cap."
Here is a .pdf copy of the instructions.
Editor's Note: Tru-Tension says "The Chain Monkey can
be used with or without the cap but we have stated to remove it before
use in the instruction as it can then be used to protect the domed nut