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If you are using the KTM system for setting chain slack, 5 mm is the tightest and 2 mm is the loosest. Going from 5 to 4 mm loosens the chain.

The rubbing you heard may have been because the chain was too tight.
 

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One other point. You didn't mention whether you measured the 4 mm at multiple points on the chain. If not, you might have found a 5 mm measurement at that time.

On another related topic, has anyone found a good simple technique to measure the 2-5 mm clearance. I've just been using my finger to feel the clearance.
 

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Thanks Colombo. I realised today that l hadn’t been getting right underneath to see where the back edge of the slider was. Just as well l looked it’s way loose. Anyone know what size in mm the axle nut is ? Love these forums, more knowledge than some mechanics l know 👍
 

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Thanks Colombo. I realised today that l hadn’t been getting right underneath to see where the back edge of the slider was. Just as well l looked it’s way loose. Anyone know what size in mm the axle nut is ? Love these forums, more knowledge than some mechanics l know 👍
32mm
 

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If you are using the KTM system for setting chain slack, 5 mm is the tightest and 2 mm is the loosest. Going from 5 to 4 mm loosens the chain.

The rubbing you heard may have been because the chain was too tight.
One other point. You didn't mention whether you measured the 4 mm at multiple points on the chain. If not, you might have found a 5 mm measurement at that time.

On another related topic, has anyone found a good simple technique to measure the 2-5 mm clearance. I've just been using my finger to feel the clearance.
You're right, my memory wasn't that great it seems. It was less than 4mm, and rubbing on the pin while on the stand. After I re-adjusted it I checked every 6-8". I'm using my brake pad thickness gauges for quick checking.
 

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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.
Please help!!! So, does anyone have a definitive answer on how to measure chain tension?I have read the 2019 manual regarding this and I think it could be better written. Maybe I'm just not smart enough. This is my first chain ever on a bike. Could someone clarify what is meant by upper chain "must be taut" in manual as on diagram label "C" ? Taut is defined I know as "stretched or pulled tight; not slack". But what is manual implying. Am I suppose to make upper section of chain "taut" before I take the confusing measurements described for chain tension? If so, how do I make it taut then "before " actually doing an adjustment at rear sprocket area? I don't think that is what manual it's asking-- correct? Or is manual implying that after you've made your adjustment between-- the chain and ""designated swingarm area for measurement of chain tension""-- that you should note the upper chain segment has become "taut" by mere act of adjusting chain tension to "2-5 mm of separation"? One more idea---Or is the manual implying that when you press your finger with upward pressure on the chain at "designated location A on the diagram", you should be pressing hard enough to make upper chain "taut" while you are ascertaining the chain tension measurement of 2-5mm between lower chain segment and swingarm area at point "distance B" from rubber guide area on swingarm. When I tried this the space between the swingarm and top surface of bottom chain segment was about 13mm as measured 2.5cm beyond the rubber guide located on the underside/ underneathe the lower swingarm area. The 2.5cm point of measurement for chain tension data aquisition was taken going towards the rear sprocket and measuring directly above the chain
proceeding upwards until contact made with overlying swingarm region "directly above " the chain. Maybe I'm doing something wrong ? I just got the bike new and it has been ridden only 240 miles, so if it was adjusted correctly during dealer prep, I would expect the chain tension now to still be close to the Manual's target values. So I assume I'm measuring at wrong point or doing something wrong.
If someone is willing to write and post a detailed description or make/post a youtube video of how to do it, I will appreciate it and I'm sure there are others who will benefit many times over. Sorry in advance for my lack of knowledge. Thanks for any help
 

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I'll take a shot at the "taut" part of your question. I believe that you are correct about pushing up hard enough to tighten the top run of the chain. That means "while" your measuring, not "before" you measure.

I believe another reason is to make sure you have the transmission in neutral while checking the tension. I have a riding buddy who's ridden since high school, 1965, who didn't know this until last year. You can imagine what that does to the accuracy of adjusting chain tension.
 

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This is not as complicated as it sounds. Put the bike in neutral, at a point 1" behind the end of the plastic chain guide, on the bottom of the swingarm, push up very firmly on the chain. If it is 2 - 5 mm from the FLAT part of the swingarm (not the ridge on the edge), you are good to go. I prefer the loose side of the tolerance, so 2 - 3 mm from the swingarm makes me happy. I also prefer to check it when the bike is sitting on a rear stand rather than the side stand (you could also just have someone hold the bike upright if you don't have a rear stand)
 

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I also prefer to check it when the bike is sitting on a rear stand rather than the side stand (you could also just have someone hold the bike upright if you don't have a rear stand)
Per the manual, p. 143, the bike is supposed to be on a rear stand to check chain tension. Holding it upright would achieve the same thing.

This brings up a point that KTM doesn't address. How much, if any, free sag is involved when setting chain tension. The chain is loosest when the shock is fully extended. The chain is tightest when the rear axle, swingarm pivot and countershaft center are in a line.

One can infer that the manual's specifications are for stock, 5 clicks, shock preload with the bike on a rear stand. That would produce a "stock free sag".

I have the shock at maximum preload and have no free sag. A very light rider may have minimum preload with more than stock free sag.

With no free sag, my measurements might be, say, 0-5 mm from the chain to the swingarm. With more than stock free sag, the measurements would surely be more than the 2-5 mm specified. I'd be surprised if it increased to 13 mm though.

Sorry to throw a wrench in this topic but I wish KTM would clarify this issue. They already have had one update going from the 2018 procedure to the 2019 procedure. Maybe they could issue one more.
 

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I have the shock at maximum preload and have no free sag.
Traditionally that'd mean you need a heavier spring.
That's a tradition unlike any other. I would think it is a requirement for proper handling when maximum preload doesn't give the proper loaded sag.

I've been looking for a heavier spring but haven't found a source. HELP! I expect no free sag in any case.
 

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That's a tradition unlike any other. I would think it is a requirement for proper handling when maximum preload doesn't give the proper loaded sag.

I've been looking for a heavier spring but haven't found a source. HELP! I expect no free sag in any case.

Hmmm... when you say "free sag" you mean the difference between when the rear wheel is lifted off the ground with shock fully extended to the motorcycle resting on the ground with no rider on it correct?
 

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That's correct. It's the only one I'm familiar with. Do you use another term?
Nope just checking. I've always set my sag by making sure that there's at least 5mm free sag. If there's no free sag, that means the spring is too soft because the preload is set too high.

If anything, the ideal sag would be set where free sag is 5-10mm, static/ride/loaded sag is 30-40mm with just rider+gear on, and the preload setting is on the lowest setting. That way you can crank it up for 2nd rider or heavier load.
 

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I'll take a shot at the "taut" part of your question. I believe that you are correct about pushing up hard enough to tighten the top run of the chain. That means "while" your measuring, not "before" you measure.

I believe another reason is to make sure you have the transmission in neutral while checking the tension. I have a riding buddy who's ridden since high school, 1965, who didn't know this until last year. You can imagine what that does to the accuracy of adjusting chain tension.
Great. Thanks for your input
 

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This is not as complicated as it sounds. Put the bike in neutral, at a point 1" behind the end of the plastic chain guide, on the bottom of the swingarm, push up very firmly on the chain. If it is 2 - 5 mm from the FLAT part of the swingarm (not the ridge on the edge), you are good to go. I prefer the loose side of the tolerance, so 2 - 3 mm from the swingarm makes me happy. I also prefer to check it when the bike is sitting on a rear stand rather than the side stand (you could also just have someone hold the bike upright if you don't have a rear stand)
Perfect. Now I feel confident about it. Thanks for the detail reply. I appreciate all who have given input. Regards
 

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Look what I found accidentally under pillion seat. A better diagram of the chain tension landmarks.
I've followed the instructions under the pillion seat on my 2020 Duke 790 , left around 3-4mm and found the chain to be way too lose. It would slap the chain guides on every bump or road imperfection. I'm lost at this point, the squeaky chain noise is gone be now but I got chain slaps everywere almost unbearable.. feels way too lose. Help please!
 
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