chain tightening

28819 Views 64 Replies 33 Participants Last post by Pingvin, Sep 6, 2021

KTM790Belgium

Discussion Starter · Apr 15, 2019

Dear duke lovers,

I kinda fail at figuering out how best to measure when i need to tighten my chain..

How do you guys do it?

Thanks!

1 - 20 of 65 Posts

Shultz

· #2 · Apr 16, 2019

So glad you asked ...

Because I’ve got no idea either!!

After 20 years on shaft driven bikes I’ve never adjusted a chain. My reading of the manual suggests that when pushing the lower run of the chain upwards in the middle it should *almost* (2-5mm) touch the swing arm. My chain touches easily so I’ve been preparing myself for an hour of skinned knuckles, swearing and rounded nuts.

Any tips from the forum would be appreciated...

Tom in Sydney

Reactions: 1

weaksy

· #3 · Apr 16, 2019

it's a tricky one... as the debate is that the output shaft issues with leaky seals may be caused by chains being too tight.

If you do it on a paddock stand as per the manual, then sit on your bike you can see/feel just how tight it then becomes... So do we run it loose at measuring... I don't know.

Mine is slightly looser now than the manual suggests.

Reactions: 1

DukeAus

· #4 · Apr 17, 2019

I have had strangers tell me i need to tighten my chain

I believe the 790 has to be run a looser i assume because it has a longer swing arm?

wozzamatta

· #5 · Apr 17, 2019

It really is pretty simple.

I put an auto jack with a small block of wood on top under the rhs foot rest, this will lift the bike and unload the rear shock so that the swing arm drops to full extension, the rear wheel only needs to be just high enough to turn. You should also put a strap around the front brake lever and the throttle so that the bike can't move forward.

I have measured on the swing arm where the adjustment point is and put a small dot of white paint on the swing arm.

Underneath the swing arm where the chain would hit I stick a piece of metal 4mm thick on the swing arm with double sided tape (this is temporary, I remove when finished)

It is just a simple matter to rotate the rear wheel and check that the chain just contacts the piece of 4mm thick metal, check about every 30cm of chain. The reason the tension is checked about every 30cm of chain is that the rear sprocket can be mounted slightly off centre which would give the effect of a tight spot in the chain - always adjust the chain in the tightest position.

Remove the piece of metal used for measuring, remove the strap around the front brake.

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Reactions: 2

KiwiDuke

· #6 · Apr 17, 2019

wozzamatta said:
It really is pretty simple.

I put an auto jack with a small block of wood on top under the rhs foot rest, this will lift the bike and unload the rear shock so that the swing arm drops to full extension, the rear wheel only needs to be just high enough to turn. You should also put a strap around the front brake lever and the throttle so that the bike can't move forward.

I have measured on the swing arm where the adjustment point is and put a small dot of white paint on the swing arm.

Underneath the swing arm where the chain would hit I stick a piece of metal 4mm thick on the swing arm with double sided tape (this is temporary, I remove when finished)

It is just a simple matter to rotate the rear wheel and check that the chain just contacts the piece of 4mm thick metal, check about every 30cm of chain. The reason the tension is checked about every 30cm of chain is that the rear sprocket can be mounted slightly off centre which would give the effect of a tight spot in the chain - always adjust the chain in the tightest position.

Remove the piece of metal used for measuring, remove the strap around the front brake.

The first sentence of your post contradicts the rest of it.
I have owned a lot of bikes and getting the correct chain tension has never been that complicated.:grin:

Reactions: 4

Rocky R

· #7 · Apr 18, 2019

My previous chain driven bikes were all dirt bikes. The way you adjusted the chain on them was to compress the suspension which would make the chain tighten. While compressed you wanted a very slight amount of play. As the swingarm goes back down the chain would loosen. Thought this would be the same...

Reactions: 4

owl

· #8 · Apr 18, 2019

Rocky R said:
My previous chain driven bikes were all dirt bikes. The way you adjusted the chain on them was to compress the suspension which would make the chain tighten. While compressed you wanted a very slight amount of play. As the swingarm goes back down the chain would loosen. Thought this would be the same...

this, leave just a bit of play when the bike is laden, it's quite slack when not compressed, although I'm a 'bigger' rider.

Chic

· #9 · Apr 24, 2019

Rocky R said:
My previous chain driven bikes were all dirt bikes. The way you adjusted the chain on them was to compress the suspension which would make the chain tighten. While compressed you wanted a very slight amount of play. As the swingarm goes back down the chain would loosen. Thought this would be the same...

Agreed. As cumbersome as it sounds, I would do this on a stand and off a stand. Sometimes I need to loosen the bolt and adjust again if it was too tight. I tightened my chain once with a friend where I left the rear axle nut loose and pulled the wheel all the way back to make the chain tight. Then sat on the bike (full weight) and had my buddy run the set screws out to the block. Then I would back them in a bit, push the block/axle up against the screws and tighten the nut. Never really had a problem with tightening the chain. Did this on dirt and sport bikes.

PitMoggy

· #10 · Apr 25, 2019 (Edited)

I had the same issue with my 790, people saying the chain was too slack and required tightening... Don't. To check tightness the manual advises checking the tension by keeping top of chain taught whilst using a finger to push bottom/middle part of the chain up to the chain sliding piece and then measure tension from there to the rear sprocket. Then when adjusted sit on the bike and check it's not tight again at the bottom otherwise the chain will be under even more tension when you ride of bumps etc. This KTM set up should look slack when on the side stand. I spoke with my local mechanic who says most of the time he slackens off chains rather than tightening them. Yes, you need 3 arms and a friend

J D

· #11 · Apr 26, 2019

For me, the past 20 years of riding motos, I find it's best to have the chain a tiny bit on the loose side, vs tight.

I've always kept at least a bit of play in the chain, (not to the point where it is straight up loose, and slapping against the swing-arm, but just a bit loose, under load), check out the specs in the manual.

Avoiding wheelies, burn-outs and launches, definitely creates less need to adjust the chain, haha.

Reactions: 4

L. s.

· #12 · Aug 25, 2019

So while checking the manual for the required chain tension I noticed an interesting thing. In the manual for the 2018 version it simply says to check the distance between the chain and the swingarm (https://www.ktmshop.se/documents/18_3213749_en_OM.pdf, page 142), but in the manual for the 2019 (https://www.ktmshop.se/documents/19_3213925_en_OM.pdf, page 144) it specifies that the distance should be measured "from the flat part of the swingarm directly above the chain, not from the edge of the swingarm". It's a significant difference, because according to '18 manual my chain is loose, yet according to '19 it's just fine.

Reactions: 1

dj790duke

· #13 · Aug 25, 2019

L. S. said:
So while checking the manual for the required chain tension I noticed an interesting thing. In the manual for the 2018 version it simply says to check the distance between the chain and the swingarm (https://www.ktmshop.se/documents/18_3213749_en_OM.pdf, page 142), but in the manual for the 2019 (https://www.ktmshop.se/documents/19_3213925_en_OM.pdf, page 144) it specifies that the distance should be measured "from the flat part of the swingarm directly above the chain, not from the edge of the swingarm". It's a significant difference, because according to '18 manual my chain is loose, yet according to '19 it's just fine.

That's interesting. Maybe that's KTMs "fix" for the leaky sprocket seals. That swingarm lip adds around 8mm in difference and KTMs spec (2-5mm tension) for each year is the same. I keep mine set to the 2019 instructions, leaning more to the looser spec.

Gotj

· #14 · Aug 26, 2019

chain tightening - a couple of observations

First, I just realized that KTM's chain adjustment procedure is like dealing with left-handed threads. One has to reverse a lifetime of practice. On all other bikes, the tolerance range has the larger number the loosest. With KTM, the larger number is the tightest. It's hard to wrap your head around this and takes careful concentration to do the adjustment properly.

Second, the recent post comparing the 2018 and 2019 chain adjustment procedures caused me to recheck my bike's chain slack.

What I found was that using the 2018 method, the chain was quite loose; the chain touched the bottom of the wear piece. It shouldn't have even gotten to the swingarm.

Using the 2019 method, the distance from the chain to the swingarm was beyond the 5mm, about 3/16", specification which means it's too tight. This has left me totally confused. I'm guessing I'm doing something wrong but I can't figure out what it is.

Gotj

· #15 · Sep 18, 2019

Here's a screenshot from the 2019 riders manual of how to set chain tension. It was described earlier but this is the official procedure.

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Reactions: 3

cster

· #16 · Oct 4, 2019

To be safe, I just set the rear preload to it's lowest setting.
Then sat on the bike to get the suspension to bottom out.
Then I adjusted the chain for a bit of play when the suspension is bottomed out,.
Then I just reset the preload (to 5 clicks for my weight) and everything seems fine.

Reactions: 2

magoo

· #17 · Feb 10, 2020

Question, l understand the 2mm to 5mm and how to measure and loosen/tighten the chain while on my rear paddock stand. On other chain drive bikes l’ve measured the slack movement in the middle of the lower chain run. Looking at the updated 2019 manual l can’t understand where the 25mm distance ‘b’ is measured horizontally from. What the heck am l missing here ?

magoo

· #18 · Feb 10, 2020

Forgot to mention that the 2018 manual pic does show measuring at the middle of the bottom run. If anyone else has their chain measured to the 2 to 5mm gap how much actual vertical play is there when you push the chain up ? All my older chains required 30 too 50mm movement. Thanks

colombo

· #19 · Feb 10, 2020

magoo said:
Question, l understand the 2mm to 5mm and how to measure and loosen/tighten the chain while on my rear paddock stand. On other chain drive bikes l’ve measured the slack movement in the middle of the lower chain run. Looking at the updated 2019 manual l can’t understand where the 25mm distance ‘b’ is measured horizontally from. What the heck am l missing here ?

Distance B is from the end of the chain guide (red arrow) to the point where your supposed to take the measurement. It's pointing you to exactly where to press up.

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Rick

· #20 · Feb 10, 2020

When I first checked mine I thought it was a tad tight, so I backed it off to what I thought was 4mm. The chain was noisy as heck, quite distracting when you're tossing it through twisties. There's a metal pin it was rubbing on below the swingarm pivot. I rechecked it this month and found it was closer to 5mm so I just added one bolt flat of tension and it came back to 4mm. I need to get back out for a fun ride to see if it's quietened up but it was rubbing less when on the stand so I'm hopeful. It seems a bit weird to be measuring the distance to the swingarm when the end of the chain guard has a hump that deflects the chain away.

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