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2020 790 Duke
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Discussion Starter · #1 ·
After searching the forum for a thread on chain adjustment and not finding any, I ran across this.


It provides some clarity regarding the ridiculous description given in the owners manual.

One thing worth noting, on most bikes when you compress the suspension the chain slack will become tighter. I noticed on the Duke it tightens up quite a bit. To see this I put all my weight on the left passenger peg then watched most all of the slack disappear. The Duke is a bike on which you definitely don't want to run a tight chain. This can lead to premature chain and sprocket wear and front sprocket shaft bearing failure, none of which is a good program.

Also something I would add to his method of pushing the wheel forward to remove slack on the adjuster bolts. I take a 10 or 12 mm wrench and put it between the chain and sprocket, then rotate the wheel until it becomes difficult to move. At this point I have a 2 foot piece of PVC pipe that I put thru the spoked wheel and bottom of swing arm so when you let go of the wheel it quickly stops against the PVC pipe. Now everything is tight against the adjuster bolts. Then tighten the main axel nut.

Hope this helps for those wondering about what the owners manual describes for checking chain slack.

Cheers.
 

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There are a handful of threads here, in the past 2 years, on proper chain adjustment.
 

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2020 790 Duke
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Discussion Starter · #6 ·
Yeah except he used the wrong method in the original manual which was too tight.
Do you mean he made a previous video that was incorrect?

Or are you referring to the video I posted as being in error?
 

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Do you mean he made a previous video that was incorrect?

Or are you referring to the video I posted as being in error?
This video he made uses the very first method when the bike was released but it was changed later on as the chain was too tight. There is an updated method in the newer manuals

He was advised in the comments but chose to leave the video up.
 

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After searching the forum for a thread on chain adjustment and not finding any, I ran across this.


It provides some clarity regarding the ridiculous description given in the owners manual.

One thing worth noting, on most bikes when you compress the suspension the chain slack will become tighter. I noticed on the Duke it tightens up quite a bit. To see this I put all my weight on the left passenger peg then watched most all of the slack disappear. The Duke is a bike on which you definitely don't want to run a tight chain. This can lead to premature chain and sprocket wear and front sprocket shaft bearing failure, none of which is a good program.

Also something I would add to his method of pushing the wheel forward to remove slack on the adjuster bolts. I take a 10 or 12 mm wrench and put it between the chain and sprocket, then rotate the wheel until it becomes difficult to move. At this point I have a 2 foot piece of PVC pipe that I put thru the spoked wheel and bottom of swing arm so when you let go of the wheel it quickly stops against the PVC pipe. Now everything is tight against the adjuster bolts. Then tighten the main axel nut.

Hope this helps for those wondering about what the owners manual describes for checking chain slack.

Cheers.
After searching the forum for a thread on chain adjustment and not finding any, I ran across this.


It provides some clarity regarding the ridiculous description given in the owners manual.

One thing worth noting, on most bikes when you compress the suspension the chain slack will become tighter. I noticed on the Duke it tightens up quite a bit. To see this I put all my weight on the left passenger peg then watched most all of the slack disappear. The Duke is a bike on which you definitely don't want to run a tight chain. This can lead to premature chain and sprocket wear and front sprocket shaft bearing failure, none of which is a good program.

Also something I would add to his method of pushing the wheel forward to remove slack on the adjuster bolts. I take a 10 or 12 mm wrench and put it between the chain and sprocket, then rotate the wheel until it becomes difficult to move. At this point I have a 2 foot piece of PVC pipe that I put thru the spoked wheel and bottom of swing arm so when you let go of the wheel it quickly stops against the PVC pipe. Now everything is tight against the adjuster bolts. Then tighten the main axel nut.

Hope this helps for those wondering about what the owners manual describes for checking chain slack.

Cheers.
Personally, I don鈥檛 find any problem at all following the manual and have never had any problem with chain tension or oil leaks from the counter shaft sprocket seal - but that鈥檚 just my experience.
 

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Discussion Starter · #9 ·
Personally, I don鈥檛 find any problem at all following the manual and have never had any problem with chain tension or oil leaks from the counter shaft sprocket seal - but that鈥檚 just my experience.
I have the new 2020 manual and it is worthless regarding chain tension.

Could you briefly describe your method. Your measurement points and amount of slack you measure to get?

Thanks.
 

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Gonna bring my own .2 cents here.. but I am on the team as the method in the manual WAY overtightens the chain. Most guys that run their chain on the "loose" side have no issues with front CS seal leakage. Honestly, i think its overkill to get out the ruler or caliper to set your tightness. When the bike is off the rear tire using a stand, i have it set so that 2-3 fingers (depending on your weight and how far the suspension sags) fit in between the chain and the chain guide. when its on the ground and I'm sitting on it, have a friend or reluctant to help wife check to see how taunt it is. It should have a light bit of slack but not a lot. If you can manage to fully compress the suspension with the help of 2 or three buddies, the chain shouldn't have enough tension to be rock solid.

Every single off road guy I know uses this method and its fine, and their suspension has double the travel maybe? and Bash the thing of rocks and roots? YES I know the angle during compression is a bit different on road bikes and yes I understand "but that's not what the manual says". If you're riding around and hear the chain slapping around a bit on the chain guide, then tighten it up. Really I don't see this as something that needs to be over thought.
 

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I have the new 2020 manual and it is worthless regarding chain tension.

Could you briefly describe your method. Your measurement points and amount of slack you measure to get?

Thanks.
The manual isn't the best I've ever seen but you just measure the distance between the chain and swingarm. You measure 2.5cm from the end of the chain guide and push the chain up towards the bottom of the swingarm. You should have between 2 to 5mm clearance.

This leaves the chain a lot looser than the incorrect method in the video. You have probably noticed threads about chain slap but it's normal on this bike
 

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Discussion Starter · #12 ·
The manual isn't the best I've ever seen but you just measure the distance between the chain and swingarm. You measure 2.5cm from the end of the chain guide and push the chain up towards the bottom of the swingarm. You should have between 2 to 5mm clearance.

This leaves the chain a lot looser than the incorrect method in the video. You have probably noticed threads about chain slap but it's normal on this bike
Hey thanks Fred. Happy Thanksgiving.
 

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Discussion Starter · #14 ·
I had mentioned that on most bikes the chain tightens up with suspension compression. On the 790 Duke this is significant.

I began my investigation by putting my knee on the left passenger foot peg. After applying all my weight 185 pounds, I checked the chain tension. It was quit a bit tighter.

Then I asked my wife to help me out. I had her sit on the bike and then I weighted the pax peg as before. This time the chain was very tight with no apparent slack at all.

The suspension was not fully compressed but perhaps at 3/4 of it's travel. I do ride on some less than smooth roads around and probably see 3/4 rear suspension travel a number of times.

So I loosened up the chain adjustment once again to compensate. Checking it again at 3/4 travel yielded some slack.

I remember reading about some reports of front sprocket shaft seal leakage. Makes me wonder if guys are running their chain way too tight has causing issue?
 

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I remember reading about some reports of front sprocket shaft seal leakage. Makes me wonder if guys are running their chain way too tight has causing issue?
There have been quite a few reports on here (search for "counter shaft" and "CSS"), especially in the first year of the bike sold.

I suspect that it has always been caused (certainly increased the incidence by) chains being too tight. I think that's why the manual was changed between 2018 and 2019.

The 2019 manual shows explicitly where to measure the gap to the swing arm on the bottom run of the chain - it's 2.5cm (0.98 inches) back from the end of the plastic slider.

When the chain is taut (top and bottom by pushing the chain up from the beneath) the gap should be 2 .. 5 mm (0.08 .. 0.2 inches). The gap is between the top surface of the bottom run of the chain and the flat part of the bottom of the swingarm (so behind the lip on the outer edge).
 

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I had mentioned that on most bikes the chain tightens up with suspension compression. On the 790 Duke this is significant.

I began my investigation by putting my knee on the left passenger foot peg. After applying all my weight 185 pounds, I checked the chain tension. It was quit a bit tighter.

Then I asked my wife to help me out. I had her sit on the bike and then I weighted the pax peg as before. This time the chain was very tight with no apparent slack at all.

The suspension was not fully compressed but perhaps at 3/4 of it's travel. I do ride on some less than smooth roads around and probably see 3/4 rear suspension travel a number of times.

So I loosened up the chain adjustment once again to compensate. Checking it again at 3/4 travel yielded some slack.

I remember reading about some reports of front sprocket shaft seal leakage. Makes me wonder if guys are running their chain way too tight has causing issue?
Which is probably why they changed the adjustment method in the manual to make it looser.
 

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Discussion Starter · #17 · (Edited)
Not to take this thread down into the weeds, I still think there is place for further comment as this procedure has caused more than a little cornfusion.

My pictures show both the area mentioned in the owners manual and the mysterious flat spot further back on the bottom of the swing arm. This flat spot only appears on the chain side of the swing arm. Humm I wonder why?

Of note the owners manual measure spot, roughly 1 inch aft of the rubber guard, is not a very user friendly place to be doing a proper measurement. This area has a taper as it moves inboard towards the tire. So if you make your measurement outboard it will be a lesser value than if you take in inboard nearer the tire. Not to mention it is hiding behind the outer part of the swing arm making a measurement a difficult proposition.

Now the flat spot further aft seems like a more logical place to take a measurement as it is flat with zero taper and is not hidden by anything. Almost as if it were designed for this very use. According to the KTM rep mentioned in the video that is exactly what it is there fore.

The place I differ with the video is the actual measurement using the flat spot. The video states 14mm which is too tight. When I loaded up the bike, significantly compressing the suspension, then adjusted the tension to have a bit of slack in this loaded position guess what the chain slack measurement at the front of the flat spot was? Right at 5mm when the bike suspension is un-loaded.

Thinking I may be on to something here.

Rim Auto part Tire Automotive wheel system Automotive tire
Auto part Rim Tire Automotive wheel system Wheel
 

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Gonna bring my own .2 cents here.. but I am on the team as the method in the manual WAY overtightens the chain. Most guys that run their chain on the "loose" side have no issues with front CS seal leakage. Honestly, i think its overkill to get out the ruler or caliper to set your tightness. When the bike is off the rear tire using a stand, i have it set so that 2-3 fingers (depending on your weight and how far the suspension sags) fit in between the chain and the chain guide. when its on the ground and I'm sitting on it, have a friend or reluctant to help wife check to see how taunt it is. It should have a light bit of slack but not a lot. If you can manage to fully compress the suspension with the help of 2 or three buddies, the chain shouldn't have enough tension to be rock solid.

Every single off road guy I know uses this method and its fine, and their suspension has double the travel maybe? and Bash the thing of rocks and roots? YES I know the angle during compression is a bit different on road bikes and yes I understand "but that's not what the manual says". If you're riding around and hear the chain slapping around a bit on the chain guide, then tighten it up. Really I don't see this as something that needs to be over thought.
I agree, personally I did some reading, measurements, suspensions compression and on and on. Then I find out that there is no need for sophisticated or headache time consuming technique. When the chain start to slap and bothers me. I just go 1/3 (1/2 max if it鈥檚 really loose ) of a turn with the adjustment bolts. I had to adjust often at the beginning but it seems to have settled now as I didn鈥檛 touch it in a while. I鈥檓 up to 12k km on original chain and counter shaft seal, maybe I鈥檓 just lucky but it seems to be working for me.
 

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2018 KTM 790 Duke, 2008 KTM RC8, 2009 Yamaha MT-01, 2008 Buell XB12Scg, 1993 Yamaha Vmax.
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This is stuck to the underneath of my seat.
Parallel Cable Wire
 
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