Swingarm eaten by chain

I hate myself right about now...



I can't tell until I get the swingarm off, but they look pretty deep.

And I have no idea how I got to this point... I'm a mechanical klutz, but I also try and stay right on top of maintenace to try and avoid having my skills put to the test.

I run stock sprocket sizes right now: 13/43, so this won't be a debate about 12 tooth sprockets. I'm more of a backroads motorcycle tourist gawking at the scenery than anything else, so not a lot of hard on/off the throttle.

I changed out my rear tire again about four weeks ago. In the process of adjusting chain tension, etc, I inspected the swingarm chain slider or whatever it is called (I'm away from home right now, from my computer as well as service manual and whatnot) as I usually do. Didn't appear to look any different than previously, still seemed thick enough. Maybe I didn't look as carefully as I should have. Chain tension was set as per spec, about 8mm below the swingarm when under upward tension.

Lubed the chain last about two weeks ago, didn't see anything unusual although I didn't look at the front sprocket while doing this. Certainly no red dust on chain.

Weather has been atrocious around here since early May, so the riding as has been overwhelmingly on the slab, not my usual riding habitat on potholed and washboarded dirt roads - so presumably, a lot less rear shock/swingarm travel happening. But with my WRR my only transport right now, I have been riding it in everything including rain and have been piling up miles faster than normal.

Coming back to the jobsite last night I felt the chain skip. Hmmm... loose chain. Just went out to deal with that, noticed that the rear chain had a deep red dust look to it. Which didn't give me a real good feeling because there's nothing like that around here for soil, but I hadn't put things together yet. Also noticed this chewed section of the mud flap, which I don't remember before, and may or may not have anything to do with this.



Anyways, got the grunge brush out, cleaned the chain up, so never got a picture of that. Adjusted the chain and found it was very, very loose. Way loose. No damaged or broken sprocket teeth that I can find. So it got that sloppy loose in very short order - possibly signalling the chain is worn to the point it will stretch rapidly from now on? That possible? The chain and sprockets are still okay, not hooked, but certainly approaching the end of their service life.

Once the chain was cleaned and lubed, I went to the front. Took the sprocket cover off, saw the damage, and positively freaked. If they sold ass-kicking machines, I'd rent one right now and use it on myself for about an hour.

So I have no idea how I screwed up badly enough for this to happen - and to happen this quickly and to this extent. I've also never had my chain go loose that quickly before, and to be so badly slack. I always torque the rear axle nut to spec, and it certainly felt that tight when I loosened it off today to adjust chain tension.

So down to the questions:

First, suggestions as to how I screwed up bad enough to do this? I've been watching that swingarm protector ever since the first reported case of this happening, but obviously I wasn't watching carefully enough.

Second, I have to run out again on the job so don't have time to start searching right now. Suggestions for places likely to have this in stock and a quick turnaround time for delivery? There's sportsplaza somewhere and a Honda place? Might as well make it someplace where I can get a new 14 tooth and 49 tooth rear sprocket with whatever bolts and a 112 link, master link chain as well... aside from approaching end of life, I don't think it did the chain any favours running in those aluminum grooves and it probably should be done on the same time. Suggestions on the sprockets to order also greatly appreciated as I'm supposed to be working here, not surfing the internet shopping.

Third, there's no Yamaha shop here and no JB weld available to throw on to protect the swingarm from being eaten further. Home, Yamaha shops and all that good stuff is about a four hour ride away on the slab. So my options appear to be to sit picking my nose and wait for packages to arrive, pay somebody going in my general direction to truck the bike back home for me, or ride it as it is for that ride.

I'd prefer to ride it home IF that can be done in some manner that won't add further damage in four hours - I don't know how thick the swingarm is at that point, but the last thing I need right now is to finish eating right through it.

The chain was adjusted to about 8mm swingarm clearance as per the Yamaha chain tension adjustment update. I rode the bike for about 200 yards, just idling along in second gear. I think I might have heard a ticking noise that might have been the chain hitting the swingarm, but at this point I don't know if it is my now hyperactive imagination or not.

With a properly adjusted chain (presumably tightened on the tight side of the adjustment scale), is it possible to ride in a manner that the conditions under which the chain would touch the swingarm are eliminated? Super smooth on and off the gas, avoid bumps that work the rear suspension as much as possible, etc? I don't know the mechanics of what causes the chain to come off the bottom of the front sprocket and pick up into the swingarm, so I'm not sure what to do at the moment.

If it can't be safely ridden in some manner, then I guess I pay for a truck ride or I sit here until some packages arrive...

Thanks for any suggestions and help. Off to work for a few hours where I'll have lots of time to work myself over for being negligent enough to allow this to happen.

Holy shit Rick... Are you back in the US or still in BC? Not sure if I can be of any help or not, but... I know with my chain once it hit a certain point it stretched fairly fast and I was having to check it almost every ride. I didn't think it would slop that fast but i guess that once it hits a certain point it just decides to let loose.

Once the lube that's sealed into the chain joints is spent, that's when you get the accelerated chain wear.
The red color of the chain was probably rust, a telltale sign of the chain joints being dry due to lack of lube.

Jäger, I'd like to know why chains are eating through sliders and swingarms, too.
I have my theories.

Do you know what your rear sag is?
This is how much your rear suspension squats with your weight in the seat.
To find out, you take two measurements from the same two points each time - one with the rear wheel off the ground, and one with you in the seat.
I measure from the center of the wheel axle to a spot on tha rear fender.

Back in camp for snackies and supplies...

YZEtc wrote:

Once the lube that's sealed into the chain joints is spent, that's when you get the accelerated chain wear.
The red color of the chain was probably rust, a telltale sign of the chain joints being dry due to lack of lube.

I was thinking aluminum oxide or somesuch... it was more like a red dust than rust on a chain, but I guess if it was rust that developed inside, got ground up, and then got outside...

But I do notice that I can move the chain sideways a fair amount and fairly easily. Without a new chain to compare it to, I don't deal with machinery enough to tell without a comparison speciman, but I don't think it should have that much lateral movement. No surprise that it is probably done... it has a lot of miles on it even though the teeth and stuff look all good.

Quote :

Jäger, I'd like to know why chains are eating through sliders and swingarms, too.
I have my theories.

Do you know what your rear sag is?

Yeah, we did that all the time with our MX bikes, so I checked it when I got my WRR.

3 1/8"- ish, measured from the swingarm directly above the center of the axle as perpendicular as possible to a joint in my rear rack. I just got my driver to help me check it again, and if it has changed in any amount, it is maybe a 1/8" - pretty irrelevant, I think. That's what it was brand new, with the Yamalink installed, so I called it good and have ran with it that way ever since... seemed close enough for my riding. I'm about 200 lbs all up with my gear on. Obviously it is more when I have my Giant Loop loaded up for a trip, but there hasn't been any of that happening much this year so far.

Yamaha calls it a Seal Guard 3D7-22151-00-00, but I don't know what seal it guards. Yamaha Sports Plaza says delivery June 27 if I order today... thats a long time be walking...

I have a ride into Whitefish, car only, I can catch Monday morning if I go that route. Hopefully Penco has one in stock. I wish I'd been paying attention to the threads about the easy way to do this without pulling much off (because of course, I was never going to let this happen to ME), but it was probably the ADV mega thread. Because if I can get a new guard before the new sprockies and chain I end up ordering get here, I'll leave off the learning experience of pulling the swingarm, doing the JB Weld fix (with prayers I don't see a hole at the bottom of those grooves) until I can do the sprockies at the same time.

Later tonight I guess I line up the suspects to call first thing in the morning to see if they have them in stock and can overnight them or second day to Whitefish or whatever.

Time to go... thanks a lot.

And when I order a chain and I need 112 links, when I specify a master link setup instead of riveted to the web store or wherever, they should send me the right length instead of me getting back out there and discovering I have to go find a nail file somewhere... right?

Silly question, how are your wheel bearings and swing arm bushings?

I usually am able to find a chain on ebay for less than most stores, web or brick+mortar. Just ordered a new RK XSO chain for $65 for example. But for me, time is usually not a factor as I tend to stock pile parts in advance of needing to change them.

The last chain I bought from Dennis Kirk, RK XSO again. I also bought steel JT Sprockets from them.

I run a rivet type master link on my chains. A lot of people run clip style master links, but I like having one less thing to worry about and I have a motion pro chain tool. If you order a 112L chain, it will be 112L with either a rivet master link or a clip master link. Do you have a chain tool available to you? Master link pliers at least?


For removing the stock chain your choices are either grind off a the rivet heads or take the swingarm off. The swingarm isn't all that involved to do, and you'll get to grease everything while you're there at least. For replacing the plastic chain slider, I think the trick is to remove the kick stand to get full access to it.

Personally I go with the 1\2" when doing my chain but that is just me--I think the wear is from too tight not too loose but only personal opinion. Anyway, that wear on the splash guard looks kind of high up--have you been carrying a passenger recently or a heavy load? Looks like it may have occured while the bike was squating. Bummer on the wear--I noticed when I went to the Sandman guard and open cover that I can see the front of the swing arm and chain slider--makes it much easier to keep a tab on than the stock cover. Hope the wear is repairable and you don't need a replacement swing arm.

Thanks for this post Jager! It reminded me that I needed to check mine. I've been meaning to do it for a while but kept putting it off. I pulled my slider and found some wear. Not as bad as Jagers obviously. But still significant enough to park the bike until a new slider arrives before the damage is worse. Here is what I found.

8600 miles worth of wear. 2000 of which I was running a 12t sprocket.


The chain has made contact with my swingarm. A small rub mark that's slightly gouged. Nothing really to worry about once the new slider is installed.

0007onWR wrote:

Silly question, how are your wheel bearings and swing arm bushings?

Not a silly question. They should be just fine, considering that the 6000 mi service was done by a Yamaha dealer, and I am rarely found in mud, sand, etc and I'm usually not riding in dust. They are about due for another look/service.

The upcoming sprocket change, now moved forward, was going to be my first shot at doing the swingarm/wheel bearings myself, and I was planning to try and line my brother up or somebody else to look over my shoulder while I was doing it. I don't know why, as I'm a better than average gunsmith and fairly handy with a lathe, milling machine, or shaper. I can make a half-assed chambering reamer or nose bored bullet mould. But put a vehicle in front of me, tools in my hands, and I just seem to have a natural ability to break something taking it apart, put it back together wrong or screw something up during the process. I seem to have hit my high point of competence back in the very early 70's working on my 125 and 250 YZ and Can-Am motors - and Cox RC engines - and have been going downhill ever since. Why is that anyways?

I'll have the shop manual, paper and electronic, and of course HighFive's website detailing swingarm and bearing how-to's, so hopefully I'll get it right first time around.

skierd wrote:

I run a rivet type master link on my chains. A lot of people run clip style master links, but I like having one less thing to worry about and I have a motion pro chain tool. If you order a 112L chain, it will be 112L with either a rivet master link or a clip master link. Do you have a chain tool available to you? Master link pliers at least?

I am a master link kind of guy. I never had problems with master links on my old bikes - but I never had fire breathing dragon bikes either. I've always been a 125, 175, 250, 350 kind of guy, and I never had a problem with a master link.

And now I've probably just jinxed myself to hell and back saying that.

Anyways, I never used to have a problem getting them on and off before with some fancy pliers work and will buy dedicated master link pliars if it comes to that. I think having to pull the swingarm to get my chain off for a good look and cleaning is a massive pain in the ass. If this original chain had been master link, and a shot chain is the root cause of this, I probably would have picked it up before if I'd had a master link chain. I've always found it easier to just pull the chain right off regularly for a good cleaning and then a good soak in chain lube.

Quote :

For removing the stock chain your choices are either grind off a the rivet heads or take the swingarm off. The swingarm isn't all that involved to do, and you'll get to grease everything while you're there at least. For replacing the plastic chain slider, I think the trick is to remove the kick stand to get full access to it.

Given the damage my stupidity and negligence has led to, the swingarm is coming off for repairs and maintenance before the bike goes anywhere again from the looks of things. And having to go this far, despite my intent to change the sprockets just before my hoped-for Idaho/Montana ride this July or August, I guess I'll be doing the sprockets and chain the same time I do the swingarm repairs, bearings, etc.

Thanks for the confirmation on the chain sizes. Always used to just replace stock stuff with more stock stuff. Wasn't really sure how it works when you just specify chain size and number of links you need.

Akasy wrote:

Personally I go with the 1\2" when doing my chain but that is just me--I think the wear is from too tight not too loose but only personal opinion. Anyway, that wear on the splash guard looks kind of high up--have you been carrying a passenger recently or a heavy load? Looks like it may have occured while the bike was squating. Bummer on the wear--I noticed when I went to the Sandman guard and open cover that I can see the front of the swing arm and chain slider--makes it much easier to keep a tab on than the stock cover. Hope the wear is repairable and you don't need a replacement swing arm.

My uneducated guess is this particular fiasco is from WAY too loose than too tight.

I set chain slack to the loosest Yamaha recommends in their updated chain maintenance sheet - about 8mm, and it is usually probably closer to 7 or 6mm. So it ain't real tight.

In fact, it is loose enough that there is a little chain wear on the front of my Sandman case saver. The chain may have been so loose the sprocket was spitting the chain against the case saver.

When I started working on the bike this morning while waiting for the helicopters to get in and the ground fog to lift, the chain was so loose that I could push one or two links up against the bottom of the swingarm. And the sprocket never skipped until yesterday. It has gotten loose enough two times before where I felt it skip under really hard acceleration. I tightened the chain immediately those times as well, and the chain was never remotely as slack as I found it today. But this time around, it didn't jump a tooth while the chain was happily gnawing it's way through my swingarm for a fair while at least.

I haven't had any heavy loads on the bike since last summer. It is possible the marks on the splash guard are not new, but I don't recall seeing them during regular cleanings after rides.. More to the point, why are their marks there in the first place? I assume the design is such that the chain is supposed to clear the splash guard to the side during suspension travel - it isn't supposed to grind against it. So is that a result of excessive side to side flopping around from a sloppy worn out chain?

trav72 wrote:

Thanks for this post Jager!

You're welcome! Happy to grind up my swingarm like a good Parmesan cheese to help you out!

I'd rather not be making the post at all, actually...

I get an easy 8-10k miles out of my steel sprockets and RK XSO x-ring chain, about double what I've gotten from the stock o-ring DID V-series chain, so +3 for aftermarket there imo. I go with a rivet link because I don't plan to remove the chain for a good looking at and cleaning every few hundred miles, I simply spray the hell out of it with WD40 every other week or three or after a big rain storm, long dirt ride, etc and keep going. When it gets really grimey I spray it down after a ride, let it soak for a few minutes, then wipe the chain off with a couple shop towels so that it looks clean again, then WD40 it again (if I know I'm going through dirt/mud soon) or with Maxima Chain wax (if I know its mostly or all street riding for the next couple hundred miles).

I'm usually needing to replace sprockets before I have to adjust the chain tension more than every 1500-2000 miles, so for me the weak link are the sprockets not the chain. Tension, I usually adjust it so that I can fit my index finger between the swingarm and chain on the underside about halfway between the chain guides and have the chain just barely touching my finger. I think it works out to 3/8" of clearance, but I don't remember how thick exactly my finger is off hand and no I'm not going to measure right now.


The guy who swapped his X wheels with me earlier today, Josh, his X has ~6700 miles on it now and the slider looks barely worn. Stock sprockets and chain, both in good shape. It kinda solidifies my theory that the terrain that you ride on, namely how often the swingarm goes above horizontal while riding at speed, determines the wear on your chain slider more than any other factor. His bike was mainly commuted on and never really worked, mine has probably bottomed out half dozen times in regular trail riding and gets works on a semi-regular basis but not as often as an aggresive rider who uses his or her WR250R as a plated dirt bike. Remember that the sprocket is above the pivot bolt for the swingarm, therefore any verticle motion of the swingarm above horizontal will drive the chain into the swingarm by necessity. The wear pattern supports this, as the majority of the wear is at the pivot followed by at the feed to the front sprocket at the front of the swingarm/slider. That section is only going to be in contact with the chain when the swingarm is above horizontal.

A 12T exacerbates the wear because of its smaller diameter causing the angle of attack of the chain at the swingarm pivot to the greater than the 13T, which in turn is greater than the 14T. Those of us who found excessive wear with a 12T probably found trails and rides that worked the suspension enough to cause the wear slowly with a 13T, but with the added angle with the 12T it gets worse. This scenario, where terrain matters most, is the only thing I can think of at the moment that would explain why lowered vs' stock height bikes doesn't show a dramatic difference, as everyone rides at a different level of aggression and on different types of terrain regardless of ride height, and why the various tensioning methods seem to have inconclusive results in regards to preventing chain slider wear.

So my point is, its likely more the fact that you beat up and down washboarded and otherwise shitty/fun roads and trails that causes your suspension to flex a bunch more and therefore wearing the slider than any inattentiveness to maintenance.

The above makes sense to me Skierd - although your sprocket life is just plain scary.

I gotta go to ground, but what I keep coming back to is how FAST this all happened. The swingarm protector was worn somewhat just a few weeks ago, but still appeared to have LOTS of meat on it. I certainly wasn't planning on waiting to the very last moment to replace it. And since then, with the crappy weather, pretty much all the miles have been on the slab - back country hasn't really opened up yet. So it happened really fast, with not a lot of swingarm action taking place on a daily basis.

Scary long or scary short? lol

Winter riding beats the shit out of a chain I've found, almost as bad as sand. Salt is the devil for moving metal, particularly mild steel, parts.

How many miles on that hot rod anyways? Still the original chain and sprocket, and if not how long on their replacements?

FWIW the wear starts earlier than you think it would, as the pivot bolt area on the slider is thinner than the rest of the slider and its in a hard to see location. You really got to get down and under and look with a light. My worn slider looked fine at the ends, but was clear through (literally, the plastic was there but thin enough to be translucent) at the pivot bolt. Once it starts digging in it'll go quickly, the material is fairly soft. A dremel melts and cuts it very quickly, assuming its the same as whats used in the stock case saver.

Also its very likely a severely loose chain flopping around doesn't help either of course. I've read several ride reports where the chain is plain worn out and stretching severely every hundred to two hundred miles when its at its very end, and it will have lots of lateral movement when it wears out as well (probably causing the wear on the mud flap). A severely loose chain might be more likely to rub on the underside of the swingarm. I never got far enough into dynamics but I'd imagine that the bottom side of the chain is under greater tension that the top as its being pulled by the countershaft (assuming a chain works like a rope where it only operates under tension loads not compression/pushing loads) and therefore a loose chain would be pulled in closer to the bottom of the swingarm, again causing accelerated wear. This might explain Yamaha's initial chain tension recommendation as well, running the chain extremely tight as a preventative measure which was corrected after printing of the manuals to the current spec as running too tight probably caused other issues...

Just my wild-assed guess.

I did some experimenting rather than thinking and the quickness of the wear MAY be attributable to the rear of the slider wearing rather than the front. I will post up some pics after they load but here is a summary of what I found.

I set mine per the manual: no weight and bike on the side stand. Set to 8-13mm. I just get it in that range using my fully calibrated finger to get the 50N upward pressure

I checked mine before starting my measurements and all was correct. Then I put the bike up on my maintenace stand which placed it vertidal with more weight on the suspension. In both cases the chain was not even near the slider. BUT as the weight moves to the suspension from the side stand the chain gets more tension placed on it and there is a very minor loss of clearance between the chain and the front of the slider.

I then tossed a ratching strap across the rear seat and hooked it to the ends of the swing arms--don't try this at home--the result of ratching the bike's suspension down (more rider load if you will) was as the swing arm comes parallel to the gound and roughly inline with the counter spocket the chain gets much tighter. What I did not see was a drastic loss of clearance between the slider and the counter sporcket.

What I did note was that the chain was putting exceptional pressure on the large aft end of the slider on the underside of the swing arm!

I then tried the same procedure with the axel moved aft more--effectively tightening the chain well outside of the recommended settings to exagerate the differences. In doing that I did note that the front slider to counter sprocket clearance vanished or almost did.

I then tried and I mean tried to compress the suspension as I had before. What I noted was that as the susension compressed the chain got tighter but the real bind was coming from the lower aft end of the chain slider! I did not get to full horizontal as I had a lot of tension on the chain with that aft end of the slider clearly being a pivot point.

From my--sophmoric--experiment it appears to me that I need to continue to do the following:
Check chain slack more frequently
Make sure I'm in the 8-13mm range--in my personal view closer to the 8 than anything else.
I need to watch the front end of the chain slider at the swing arm pivot.

More importantly I'm going to pay a whole lot more attention the the lower aft rear of my chain slider. My assumption is--and you know about assume--as the chain wears the slider it wears the aft end first--it is thick and takes a beating. This occurs mainly due to the chain being too tight--again in my humble opinion.
As the aft lower end of the slider wears it lets the front come closer to the swing arm and when the front begins to wear it goes fast as it is not nearly as thick as that lower aft rear. I've got a new one here and mine measures 1\2 inch at the lower front and over 3\4 of an inch at the lower aft rear.

On side stand chain adjusted per owners manual shot of the slider swing arm clearance


Sitting vertical--weight on suspension--on maintenance stand chain adjusted per owners manual




Suspension "loaded" swingarm near horizontal--chain slack per owners manual


Chain way too tight suspension loaded


What was keeping the small gap at the front of the lower slider? Me thinks the aft rear lower slider. This is a shot bike on side stand, chain correctly adjusted, no weight on suspension. Note how the aft lower rear of the slider will hold the chain out from the swingarm and how it tapers to the smaller front edge at the swingarm.


I would be interested to hear if any of you still have your old slider--and swingarm damage--was that aft lower rear worn and if so how much? I'm guessing it would wear to about 1\2 inch and then the front would start to wear rapidly--just my guess.

The lineup is deep for the internet station tonight.

Skierd, about 7000 miles on this chain/sprockets set - all replacement OEM parts changed out together all at once.

My practice was to check by pulling the case saver & guards and actually check by sticking my little girlyman fingers in there while eyeballing it with the tac flashlight. Only added a couple of minutes to a chain lube & tighten session.

That's what pisses me off - I checked that bastard religiously while doing maintenance after seeing the first pictures of damage like that. And now I'm the poster boy for it.

Akasy's observations are interesting. I guess the solution is to have a spare seal guard around, just like you keep extra oil filters and o-rings around, on the assumption that one day "it's time". I'd been wondering how soon before the day I'd look and go "Yup, time to change the chain slider out". Obviously, I should have been listening to my spidey-sense, even though all appeared well.

Thanks for the comments guys. Supposed to get up over 70 for the next few days, first time this year, and if we get back to camp in time I'm going to be sitting around just staring at my wounded bike.

Later...

Okay - I'm just throwing some thoughts out there for chewing on.

I've been riding since 1985-ish or so. Exclusively on street bikes. Mostly crotch rockets.

Old school rule of thumb was always that if you ever were to error on the side of caution go a little looser, rather than a little tighter.

Also - half-inch to inch of deflection was where you wanted to be.

That was on street bikes.


I find it hugely improbable that 8 mm of deflection is anywhere near enough on any X or R where the suspension travel is two to three times greater than a street bike. (I know - how dare I question the great and mighty Yamaha designers and engineers)

I'm wondering, especially since Jager has stock gearing and sounds like he's much more diligent with his maintenance than I have ever been, if the cause here might be too tight of a chain.

I know that sounds counter-intuitive - but it's something I ponder.

How can a bike with 10 inches of suspension travel start with only 8-13mm (half an inch) of chain slack in a completely un-weighted condition?

I would think you'd use up that slack just by sitting your weight on the bike and having some reasonable amount of sag set, let alone when you actually start using the suspension in harsher conditions.

Does a half inch of slack in an un-weighted condition seem way too tight for a bike with 10 inches of travel to anyone else?

I say this because I am probably much closer to being in the 3/4's to one inch of "slack" club with my chain, and I have about 7500 miles on my X with no signs of swing-arm destruction as best I can tell.

This weekend I think I'll lay my bike over on it's side so I can get a much better look at the underside of the swing arm.

motokid wrote:

Does a half inch of slack in an un-weighted condition seem way too tight for a bike with 10 inches of travel to anyone else?

Yes, indeed.
Way too little free play.

However, if I read the updated chain adjustment bulletin that Yamaha Motor Corp. released correctly, they're making things a little confusing by specifying you push upward on the lower chain run with a certain amount of force, where you should then have the chain positioned 8mm-13mm from the bottom of the swingarm.
It's not 8mm-13mm of slack, but the chain should stop 8mm-13mm from the swingarm.
The bulletin even shows a geek-approved gauge you should be using in order to measure the force used to push the chain upward.

Here's a link to the bulletin:

http://rickramsey.net/MTpdf/TechnicalBulletinM2008-020short.pdf

My opinion on the whole chain slider matter, and chain slack/adjustment, in general:

Generally, most riders adjust their chains too tightly.
I think most riders feel that their chains adjusted to allow adequate slack with the swingarm moved upward will look too loose to them because they are not familiar with how it should look with the swingarm nearly fully extended (as when the bike is parked on the side stand).

I believe the reason for this is that they're worried of chain derailment (chain jumping off the sprockets), and/or don't like driveline lash or slop, and/or don't realize that chain freeplay will decrease as the swingarm moves upward toward aligning the front sprocket, swingarm pivot, and rear wheel axle all in a straight line.

Believe it or not, I've owned more than one Yamaha motorcycle where the chain slack spec. in the Owner's Manual was too little to allow some free play with the swingarm moved upward.
That's right, folks - the official spec. was not a good one.
I haven't bothered to experiment and see if this new and official chain adjustment spec. is good or not because I simply do it my own way, anyway, and that's making sure there's sufficiant slack with the swingarm moved upward and aligning those three points mentioned above.

Myself, I find it hard to believe that a chain that has too much slack in it is eating throught riders' chain sliders and then swingarms.
No, I believe that the chain is not just slapping against it, but being forced to saw through it while under some considerable tension and force.
The riders just don't realize this as it's happening.

The easiest way I've found to see the chain slider is while looking under the bike from the right-hand side.
Use a flashlight.

Old, original spec:





So how different is the new "chain spec" with the 8mm from swing arm to the original?

Is the new spec tighter, or looser?

I am showing 11,605 miles.
Still the original chain slider with minimal wear.
Included a pic to show how I check my chain slack and where I keep it.

Do you have a lowering link?
Not saying they cause this...but something I have wondered about.

Since I just set my chain per the specs I will measure today and see how it compares to the old spec.
As to the 8mm in the new spec--that is acutally more chain slack than the other end which is 13mm. Since the measurement is done on the side stand with the suspension unloaded the chain is "hanging down" if you will. As you press upward you measure from the chain to the bottom of the swing arm--8mm would be closer to the swing arm--13mm would not be as close--or in other words at 13mm the chain is tighter, does not move upward as much and at 8mm it would be looser, moves up a greater amount from the static postion.
As I said my personal option is to run that puppy looser as I have for most of my bikes over the last--umm let's say 45 years. I agree with YZ that running tight appears to be what wears the chain slider--first at the rear then very quickly at the front as the rear edge wears down. I'm running -1 tooth on the front and stock rear.

yeah...I always forget that the "new" measurement method is the distance from swingarm to chain.

So smaller distance is actually more slack.

I just went out ("non-smoking smoke break") and checked my slack with a non-calibrated eye and a pretty hefty push on chain. I got to roughly a half inch-ish from chain to swingarm. Looked a little less than a true half inch but not much.


Thinking more about this:

Would swingarm wear on underside of swing arm be a symptom of chain to tight, and swingarm wear on top be a symptom of too loose?

The tension on the chain under load (acceleration) would be on the top part of chain between sprockets right?
The slack would be under the swingarm during normal operation.

But when the suspension compresses the chain on the top move away from swingarm and the chain underneath moves closer, or even into the swingarm.

Just trying to figure out cause and effect here while sitting at desk.

What would too loose versus too tight chain conditions look like on swingarm protector?