Swingarm eaten by chain

Well it’s defiantly the wheelies. Now I have to figure out how to correct it.
I put a new slider on this weekend and did about 100ml of dirt, trails, jumps and a little street. The slider looked new. Three wheelies later I have grooves down the front halve of the lower slider.
When pushing the chain up to the swingarm it’s damn near hitting it. Not hitting it but close, about ¼ inch.

so has it been determined that a loose chain or tight causes this, or is it just the nature of the beast?

I don't see how a too-loose chain can grind through the slider and then the aluminum swingarm as chain sliders are designed to take a lot of sliding and slapping from the chain.
Seems more like a tight chain being forced to grind through it while under tension.

YZEtc wrote:

I don't see how a too-loose chain can grind through the slider and then the aluminum swingarm as chain sliders are designed to take a lot of sliding and slapping from the chain.
Seems more like a tight chain being forced to grind through it while under tension.

I agree.

A loose chain hitting slider will conform to the largest area it can and distribute the wear over a greater area. A tight chain with eat through a smaller area faster by concentrating that friction onto a much smaller spot.

so what kind of tension should we be running?

oldschoolsdime92 wrote:

so what kind of tension should we be running?

This is the revised chain tension guide from Yamaha for the WRR/X.

Best way to figure it out is to put the swing arm pivot point, rear axle, and countershaft sprocket all in a straight line. You can do this by putting the bike on a stand and removing the link from the rear shock and using a ratchet strap or cam lock strap lift the swing arm till everything is in aligned. This position is the furthest that the chain will need to stretch. At this point set the chain so there is about 6mm of slack.

Remove the strap and put everything together again and drop the bike on the side stand an measure the play for future reference.

This works for any sprocket combo whereas I believe the manual is meant for the stock sprocket set up and may or may not work for other combinations.

My experience with this stuff:

When I sold my 2008 WR250X in July of 2011, the buyer wanted me to install the original shock spring before he took delivery of the bike (I was using a softer spring as specified by Go Race Suspension when they repaired and revalved the leaking shock that I discovered when I bought the bike used in December 2010).
To change springs, I left the shock absorber in place and unbolted the bottom shock mount from the shock linkage and removed one of the linkage bolts and let the linkage hang down out of the way, allowing me to slip the spring off and on from the bottom.
I left the rear wheel in place and as it was when I was riding the bike.
It was a time-saver.

While the swingarm was free to swing through it's entire arc of wheel travel, I observed what happened.
I found out that with this bike, even when there is enough slack to allow the above procedure (posted just above this post) to pass with flying colors, if you were to move the swingarm through it's full arc, when it gets toward the last few inches of it's travel the chain will be resting on the chain slider and making solid contact.
The point of most pressure was at the front of the slider since when the swingarm is near bottom the forward edge of the slider hangs low, even though it made contact down practically it's entire length.
This is why when you see pics of eaten sliders and swingarms, the grinding marks are at some weird angle.

I believe what had always prevented me from having any issue with this on my WR250X (and WR250R before that bike) is that my dirt bike background has me running plenty of chain slack due to off-road conditions - anybody who rides dirt bikes a lot has gotten dirt caught between their chain rollers and the sprocket teeth and the resulting bowstring-tight chain that comes with it.

In other words, I believe that even if you think you have plenty of slack, you actually may not have enough near the end of the suspension travel when the chain slider rotates and the forward edge sticks down.

This is due to, I believe, the swingarm pivot on this bike being a little bit lower than average compared to the front sprocket.
This magnifies the effect of the slider sticking downward as the swingarm moves.

If you have enough slack for this condition, you'll never have a problem.
If you don't, your chain will be pressed firmly into the chain slider at the forward edge (not just resting on it as it should, but forced into it) and will wear through the parts when the swingarm is near the end of it's travel, and the less slack there is, the earlier in the swingarm travel contact will be made.

I have also found out that most riders tend to run chains tight.

oldschoolsdime92 wrote:

so what kind of tension should we be running?

With bike leaning on sidestand - simply find the center of the chain under the swingarm, and push the chain up towards the swingarm.

What's the gap between the chain and swingarm when pushing up with a decent amount of force?

Chain touching swing arm means you might be loose.
A gap of more than 1/2 inch means your probably too tight.
I try to keep that gap somewhere between 1/4 and 1/2 inch.

I'm on an X, and do 99% riding on paved surfaces, so my suspension rarely gets compressed to it's limits.

Also - some wear on the slider is normal. Not to be feared.
That's why it's there. Just check it when you change oil, or every 1000 miles.

I sometimes get the impression that some members here think any wear marks at all on the slider means something is horribly wrong.

Mine lasted almost 10,000 miles. I replaced it before it was completely worn through.

Just checked mine and because the chain was a little more cleaner than normal. Found it was way to tight.  No damage to the swing arm, just going to check it more often.  I already have a replace guard, so I am good to go.

Am I correct you don't have to remove the swing arm to replace the guard with a new one?

beefcakemorris wrote:

Am I correct you don't have to remove the swing arm to replace the guard with a new one?

Correct.

Re; Dirt Bikes

Can't recall where I read it but a study was done by factory mechanics at a large top amateur moto and they found that nearly everyone's chain was too tight.

gatorfan wrote:

Re; Dirt Bikes

Can't recall where I read it but a study was done by factory mechanics at a large top amateur moto and they found that nearly everyone's chain was too tight.

I'd bet your house that if you looked at the chains of guys who've come from mostly a street riding background, it's FAR worse.

I'm a new member and having read about this on this forum, and also about it on ADV, I decided to creep out in the garage in the cold and dark, and have a look at mine. The bike was bought recently with about 7k on the clock and a completely knackered chain and sprockets (never changed from new by previous owner--Scottish Police!!) . I changed the front sprocket to a standard 13 tooth Yam with rubber bits--but never thought to look at the BOTTOM chain slider. The top was a bit worn as usual but I've gone for a 52 rear so I thought that this would hold the chain off a bit more.

Anyway, I had a good look at the bottom front of the slider and sure enough its worn away and there are signs of SA wear. When you look at the arrangement with the bottom roller guide the chain is pretty well controlled, and even when the soft rear spring is fully compressed the wear marks still seem to be more round the front of the SA than I would expect, or have thought possible, simply by angle changes.

In my opinion a tight chain certainly won't help, especially with a 12t front---running tight at highway speeds would probably wear the slider away (as shown by some pics of a more longitudinal wear pattern)--and even if you are doing jumps the chain won't be spending much time contacting the front edge of the slider on landing(and its "slow" speed). In my case the marks are so far around the front that I think its caused by a really slack chain hanging on to the sprocket--especially at highway speeds--and being thrown up against the slider. I think the answer is a well lubed chain without any tight links--and the correct adjustment. A tight link will get a "set" as it passes around the gearbox sprocket and then , without bottom run tension, will naturally flow up on leaving at the bottom--retaining the kink--and will fire straight into the front edge of the SA. Its almost worth adding a titanium strip to the new slider to stop the wear!--I have some and might try it.

I'll change the slider now!!

also just found this--this is real wear!

http://supermotojunkie.com/showthread.php?145948-Go-check-your-chain-slider-on-your-wr250x!

Looks like I might have just saved it

Damn! Now you guys have me worried! I have an 08' WRX that I bought new in 10'. I put about 15K miles on it commuting but now that I have a dedicated street bike I want to use this for more play/practice and convert it to more dirt/dual sport oriented.
I looked at my chain last night and it seemed fine (but that was on a stand). I took it off the stand and used a tie down strap to compress the suspension and holy crap the chain is crazy tight. I loosened it up and have about a 1/4" b/t the chain and swing arm when pressing up on it when the suspension is still compressed, but it seems super loose now after taking the tie down off. It almost has me a little worried but I guess after I'm sitting on the bike and riding the chain should have some of the slack taken out. Also, thankfully I bought a chain alignment tool b/c the hash marks on the swingarm seem kinda off.

Well damn! I just checked my swingarm and and it started to eat through it. It doesn't look that bad and that is surprising for 15,5xx miles on it. So I am going to order a new slider. I think I read somewhere on here that the entire swingarm has to come off to replace but I also read that is not true.
Any install instructions that anyone can offer?

NOT AT ALL.
I checked my slider a few weeks ago by pulling it off, inspecting it and putting it back on. The only thing I had to remove was the stand (2 bolts on frame).

Evol wrote:

NOT AT ALL.
I checked my slider a few weeks ago by pulling it off, inspecting it and putting it back on. The only thing I had to remove was the stand (2 bolts on frame).

Really is that all?! That would be awesome! I just ordered the chain guide slider so I hope to have it soon. I was really dreading having to take the swing arm off.

Glad I started reading this thread.  Here is mine after about 15000 miles and probably way too tight of a chain the entire time.  The swing arm isn't terrible so thank God for that.

Got a new slider. The picture shows the bottom side of the slider where most of the damage was done.

I've been bit by the chain eating the swing arm issue. The local welder was able to repair the damage, which went as far as touching the bearing. So, with a new chain slider, properly adjusted slack ( removed shock from linkage method ) I've ridden about 1,000 kms. I checked the slider for the first 150 kms at different intervals, all seemed well.

After the last ride, checked the slider and observed extreme wear on the front bottom. The chain is suspect at this point, so I've ordered a replacement set to see if it helps. Also, applied epoxy to the slider, hoping it lasts for a few rides.

I was thinking. The bike is a 2009 WRX, setup with a 21" front, and 17" rear. Would this setup alter pivot points and help contribute to more slider wear?

ACR wrote:

I was thinking.  The bike is a 2009 WRX, setup with a 21" front, and 17" rear.  Would this setup alter pivot points and help contribute to more slider wear?

That wouldnt make any difference at all.

Lowering the bike or riding with a heavy load on the rear so the rear sags down more then normal puts the chain closer to the slider tho as the chain touches the slider when the suspension is bottomed out and is very close to it when compressed 1/2 way or more.

Quote :

That wouldnt make any difference at all.

Lowering the bike or riding with a heavy load on the rear so the rear sags down more then normal puts the chain closer to the slider tho as the chain touches the slider when the suspension is bottomed out and is very close to it when compressed 1/2 way or more.

Thanks for the insight.  I recently lowered her using the stock adjuster, as low as it would go.  Perhaps I should raise it back up to mid level+ and see if it helps?  

ACR wrote:

Quote :

That wouldnt make any difference at all.

Lowering the bike or riding with a heavy load on the rear so the rear sags down more then normal puts the chain closer to the slider tho as the chain touches the slider when the suspension is bottomed out and is very close to it when compressed 1/2 way or more.

Thanks for the insight.  I recently lowered her using the stock adjuster, as low as it would go.  Perhaps I should raise it back up to mid level+ and see if it helps?  

yes that will do it.....

Quote :

yes that will do it.....

Alright.  The new chains and sprockets will be here by the end of the week, I've gone with 14/49 this time.  I'll raise the bike back up, install the new goodies, and take a nice long ride.  Will report back with the results and some photos.  

Thanks for the help.

just changed my slider out at 18,000 miles, it was just barely worn thru and hadn't touched the swingarm yet, so you want to get the slack just right, easy take a tie down strap and hook it on the swingarm and across the seat or fender while sitting on the seat pull the strap tight and get the swingarm in line with the c/s sprocket this with get the chain at its tightest point and give the chain a little slack when you pull the strap off you can then see how much slack you actually need and it does seem pretty loose but that's how much you need, too tight and you are wearing out your entire drive train and bearings in the engine