How to Measure Chain Slack?

[Cjanssen83]

Which point do I measure from? Red, green, or blue?

And I go diagonally, not straight down, yes?

How much pressure should I be putting on the chain with my finger?

 The manual and the service manual are kinda vague in my opinion. 

It’s a bit jerky at times shifting gears, like it’s trying to catch up…assuming tightening my chain will help?

Edited May 21, 2023 by Cjanssen83

[sweetscience]

Measure slack at the tip end of the second crest.  Just left of where the green mark begins.  You can check this by measuring the midway point between the front and rear sprockets' chain contacts.  Measure slack perpendicular to swingarm.  Put as much pressure on the chain until it can no longer stretch, which is not much.  The important rule is to measure slack at the TIGHTEST point on the chain, as you will see there are loose and tight spots.  So, I go with a 56 mm slack at its tightest spot on a paddock stand.  Or 51 mm with the bike on its side stand.

Happy trails! 

[ElGonzales]

Blue, shows the drawing in the user manual, using the sidestand.
15N pressure with the finger (or whatever) to the chain, says the user manual. 15N = 1,52 kg   (15N / 9,81 m/s^2)

 

[sweetscience]

Yes, I stand corrected, the blue zone is the right choice.  +1 to ElGonzalez.

The rollers on the chain will contact the track of the chain guide first. 

 

[Cjanssen83]

Ok, so blue mark. I think I did it from green last time. 

Cheers, mates!

[Cjanssen83]

5 hours ago, ElGonzales said:

Blue, shows the drawing in the user manual, using the sidestand.
15N pressure with the finger (or whatever) to the chain, says the user manual. 15N = 1,52 kg   (15N / 9,81 m/s^2)

 

How do measure Nm with finger pressure?

…I googled and found that 1 Nm is like holding an apple, so I just push down on the chain with the force of 15 apples?

…I feel like I’m in elementary math class again, lol!

[ElGonzales]

N is not Nm   

The pressure - force  you should put onto the chain is 15N, which corresponds to a weight of 1.52 kg. Thats the weight of  ~1.5 liters of water.
You can convert it in any other unit of measurement, 3,30693 pounds for example.

Don't blame me, thats the instruction of Yamaha and you asked the question

Kick the chain up with the tip of your boot, if  it moves approx. the width of a cigarette box chain slack is allright, this is my method  

[Pursuvant]

2 hours ago, ElGonzales said:

Don't blame me, thats the instruction of Yamaha...

...Kick the chain up with the tip of your boot, if  it moves approx... width of cigarette box...chain slack is allright, this is my method  

So much yes here for the cig method

Kudos to @klx678 as a source, he checked the perpendicular distance with swingarm at bottom & top of travel, because he knows manuals have been wrong in the past.

[crakerjac]

A smiling chain is a happy chain.

[7fold]

Another tip for chain slack I read here a while back (I don't remember who posted it to give them credit, unfortunately) is that you can use a credit card to measure. The manual calls for slack between 51-56 mm (or 2.01-2.2 in) and your typical credit/debit/gift cards are ~54 mm (or ~2.1 in) so almost the middle of proper slack. 

[Triple Jim]

I have  a wedge of wood I cut so at one end the chain is at 2" slack, and at the other end it's at 2.2".  If the 2" end goes in, but it doesn't go all the way though to the 2.2" end all is good. 

You just have to cut the wood at the slack specs minus 1/2 of the chain width.  With the stock chain, that's 1.71" at the short end and 1.91 at the long end.

 

 

[FZ not MT]

Right or wrong, I've been using the blue line - When I push the chain up toward that lip, if it touches the lip, it's time to tighten the chain.... seems to work for me. 

 

[Triple Jim]

4 minutes ago, FZ not MT said:

Right or wrong, I've been using the blue line - When I push the chain up toward that lip, if it touches the lip, it's time to tighten the chain.... seems to work for me. 

 

That's actually a pretty good way to check it.  I just adjusted mine today with my wooden block, and if I use one finger to press the chain up pretty snugly, there's just about 0.2" of clearance.  More fingers and I can make it touch, so the one finger thing is relevant.

[shinyribs]

If in doubt, make it looser. It won't hurt anything. Talked to a young guy once that was terrified of letting his chain get to loose and worried it would derail, get tangled and make him crash. Reddit had him worried to death. 

 

Unless your chain is obviously drooping like this, it's never gonna derail from being a bit loose. You're fine.

[mt7fan]

Blue line. Difference between measured on centerstand and sidestand is 2 mm. 

[DewMan]

15 hours ago, Triple Jim said:

I have  a wedge of wood I cut so at one end the chain is at 2" slack, and at the other end it's at 2.2".  If the 2" end goes in, but it doesn't go all the way though to the 2.2" end all is good. 

You just have to cut the wood at the slack specs minus 1/2 of the chain width.  With the stock chain, that's 1.71" at the short end and 1.91 at the long end.

 

I like the Go/No-Go  gauge functionality of your wood block. It's very much K.I.S.S. method.  I'm gonna make my own now. Thanks for the idea Jim. 

[Erci]

Resurrecting this thread due to new findings. I just replaced the rear shock and while I had it out, I figured I might as well check chain tension throughout full rear wheel travel. I moved the wheel up 130mm from fully extended position (using center of rear axle and fairing bolt under tail as reference point). The chain was actually looser under full compression.. not tighter. I then measured tension throughout full travel range. At no point did the chain feel any tighter than it does when the bike sits on the sidestand.

I've always been taught that it's better to have it too loose than too tight and sure that still makes sense, but it also seems there's no point running it needlessly loose, because the looser the chain is, the more it exacerbates driveline lash going from closed throttle to open. 

This brings me back to original post with "where to measure slack". If you go with 51mm at the blue line, it's much looser than it needs to be, based on what I'd just observed. 

The other (in my opinion simpler) way to "feel" the right slack is to push the chain UP at the blue line. Mine was very close to making contact with the way I had it adjusted previously. I've tightened it up a bit and now have about a 5mm gap at that point when I push the chain up.

[klx678]

If one wants to know fairly precisely how to check chain slack here is a method to be certain. 

• rotate the rear wheel to find the spot in rear wheel rotation that the chain is tightest (caused by eccentricity in the sprockets)
• either removal of the rear shock or pulled upward using a tie down through the back wheel and over the seat/subframe pulling the wheel upward until the rear axle, swing arm pivot, and counter shaft centerlines are aligned.  
• adjust chain for around 1/2-1 inch (around 15-25 mm) of slack at that tightest point in rotation of the wheel.   I'd measure mid-swing arm, which is probably about what Yamaha has in the manual.  
• once one has adjusted to that setting, release the suspension or put the shock back on or remove the tie down and, with the bike on the side stand or swing arm stand unloaded, measure the slack to see what that unloaded measurement will be.
• that will be how much slack should be adjusted in the chain when, not tighter.   

That is one key point, a shade loose is better than too tight.  

[Erci]

6 hours ago, klx678 said:

If one wants to know fairly precisely how to check chain slack here is a method to be certain. 

• rotate the rear wheel to find the spot in rear wheel rotation that the chain is tightest (caused by eccentricity in the sprockets)
• either removal of the rear shock or pulled upward using a tie down through the back wheel and over the seat/subframe pulling the wheel upward until the rear axle, swing arm pivot, and counter shaft centerlines are aligned.  
• adjust chain for around 1/2-1 inch (around 15-25 mm) of slack at that tightest point in rotation of the wheel.   I'd measure mid-swing arm, which is probably about what Yamaha has in the manual.  
• once one has adjusted to that setting, release the suspension or put the shock back on or remove the tie down and, with the bike on the side stand or swing arm stand unloaded, measure the slack to see what that unloaded measurement will be.
• that will be how much slack should be adjusted in the chain when, not tighter.   

That is one key point, a shade loose is better than too tight.  

Yup, basically very close to what I did, but it was interesting to learn that the chain does not keep getting tighter throughout full travel. It felt tightest at static sag. Of course, never want it to be too tight, but I just wanted to mention that when the bike is on sidestand and you can push the chain up where it makes contact with the chainguide, it's more loose than it needs to be. It will work, but you'll feel more of a "jerk" going from off to on throttle. 

[klx678]

I have the same experience with some snatch when going off to on throttle.  I live with it no problem, I had a chain that broke on my 550 Zephyr, from being too tight.  Not a good experience, but at least I was close to home and nothing was horrendously damaged.   So I would rather be a shade loose than too tight.   Could have damaged bearings or broken something with the Zephyr.

You are right, it shouldn't hit the swing arm.  Like I said, I think it was around 2" of slack total, not one direction.