Instant chain stretch?

[Squareman357]

Ok heres the deal. I was getting ready to merge into traffic coming back from Kentucky and I hit it a little hard. As I shifted to third felt a strange shuddering. I rolled off a bit, shifted up to fourth, and it was gone. Back to third, nothing, so I shifted up again and went on my way. Gassing up I checked the chain and everything looked fine. At the next gas stop, I forgot to zip the sides of my pants and reconnect my audio, so I pulled over under an overpass and fixed up myself. Getting back on the road a truck was coming, so once again I rolled on a bit hard and shifting to third I felt the shudder again. It dissapeared as soon as I shifted, and after turning off the music and listening, i didn't hear anything amiss. Some 400 miles later I pull up in front of the house and dismount, and lo and behold the chain is practically laying on the centerstand. There has to be at least 4 inches of free play vertically in the chain now. I unloaded all my gear and sat on the bike to see how much slack it would take up and it was nearly none. I slowly rode it around the block to the garage and put it away, and it seems like everything is still connected and all the sprockets still have all their teeth. I will definitely need a new chain, and possibly new sprockets, and from the looks of it I was lucky to make it home.

Ok here are the questions. What could cause something like that to occur? Do I need to be worried about my gearbox? As of my arrival home the chain has 14,350 miles on it and is the stock chain, as are the sprockets. The rear sprocket isn't shark finned and has normal wear. When I say rolling on hard, I don't mean redlining, but I did run it up to about 8 or 9k before shifting. So...thoughts?

[John01XX]

Check to see if the rear axle has loosened up and moved forward hence slack chain.

Might just have to properly adjust the chain back up and tighten the axle bolt and Ride away, hopefully.

[Squareman357]

Checked that. All rear bolts, cotter pin, etc on the rear axle seem tight, at least by hand. I couldn't move the wheel around any. If I loosen and adjust, the chain will be well past the red markings on the chain gauge.

[Guest rockmeupto125]

I might ask....when is the last time you checked it? I didn't notice THAT tidbit in your post.....

[Squareman357]

Well I lube it every 500 miles or so, so I check it often. I had new shoes put on her a couple weeks ago, and it was adjusted then to take up slack, while still being well in the green. I also checked it at both my fuel stops on the way home and it wasn't hanging like that then. No kinks, or binding, and it was pretty quiet when turning the wheel.

[Guest rockmeupto125]

the only thing I can imagine is that

1.you stripped some teeth from the sprockets..shortening the path the chain had to follow

2. the wheel slipped forward despite feeling tight at present.

3. the shock against the chain ruined many of the link bushings and in effect, made the chain longer. Is it the same all the way around, or does the slack vary when you turn the wheel?

[Northman]

Cotter pin?

I don't have a cotter pin :?

I agree with John that the axle probably moved on you. Try torquing the axle, and see if it tightens any. Re-adjust your chain, and try a test ride.

If you have kinking/tight spots in the chain, replace it. Otherwise, keep going

[Pete in PA]

Any signs of brick red rust powder on the chain? Once the o-rings give up the ghost, the chain will stretch THAT fast.

The mileage is a little low for the chain, but not much. I bet it's a RK chain.

With a flashlight form the rear you can see the front sprocket and at least see it has all its teeth.

I would adjust the chain, tighten the axle nut to 69 FT-LBS, turn the adjusters tight against the axle, and take it for a ride.

If the chain IS shot get a DID 530 ZVM and enjoy a 25-30K mile chain.

[Squareman357]

the only thing I can imagine is that

1.you stripped some teeth from the sprockets..shortening the path the chain had to follow

2. the wheel slipped forward despite feeling tight at present.

3. the shock against the chain ruined many of the link bushings and in effect, made the chain longer. Is it the same all the way around, or does the slack vary when you turn the wheel?

Slack appears the same all the way around. When I get home tonight I'll take a flashlight to it and see if the front sprocket is missing any teeth. I'll also grab some tools and see if I can tighten the axle nuts any more than they are. Thanks for the ideas guys. I was going to get a new chain and sprockets before California anyway, this just pushed up my time table.

Pete, I don't see any brick red rust powder on the chain, but the lube may have absorbed that. The chain looks dark gray or black and the side plates don't show any rust either.

North, there is a large cotter pin back there, at least I think I remember one being there. I'll check that when I get home from work as well. Maybe I was so in shock at the state of the chain I was looking at something else.

[N1K]

I'll also grab some tools and see if I can tighten the axle nuts any more than they are.

Make sure one of those tools is a torque wrench.

:oops:

[Redbird]

Before you go snapping your axle trying to get it tight enough not to move, remember that the ajuster plates are what should keep it from moving, not torquing the shit out of the axle nut.

If everything seems to be in good order, ajust your chain, tighten the axle, then snug up the 8mm ajusting nuts by turning them outward, not in. I've seen a few guys chain problems disappear with that small piece of advice.

[Guest rockmeupto125]

then snug up the 8mm ajusting nuts by turning them outward, not in. I've seen a few guys chain problems disappear with that small piece of advice.

Not to disagree with the device, but just a warning to be cautious with this. That's a steel bolt in aluminum.

[N1K]

That's a steel bolt in aluminum.

And lemme tell you what happens with steel bolts in aluminum!

[Redbird]

Not to disagree with the device, but just a warning to be cautious with this. That's a steel bolt in aluminum.

Agree. Note the use of the term "snug up" rather than "have Nik come over and tighten them until they quit leaking". :wink:

[N1K]

"snug" is such a relative term.

[Pete in PA]

I have to disagree Redbird.

the 8mm bolts are for adjustment/allignment only. Once you tourqe the axle nut to 69 ft.lbs. you can screw them out and throw them away. the axle is going nowhere.

If you have a cotter pin back there THAT'S your problem. Someone swapped in some non-factory parts.

[Redbird]

Once you tourqe the axle nut to 69 ft.lbs. you can screw them out and throw them away.

Try that and let me know how it goes. Do you really think you can apply 130-140 horsepower and around 80 foot pounds of torque to big bolt in a slotted hole without pulling it forward?

[Pete in PA]

If the adjusters were designed to hold the axle in place they would be a LOT more heavy duty then little 8mm bolts. They would also have locknuts on them.

[Squareman357]

Haven't had a chance to have a go at this yet, but I should today since I get off early. LOTS of new info here for me to look into. Thanks. One of these things has to be the solution. I DID get a chance to look for the cotter pin, and that wasn't on the axle bolt, nor the 2 chain adjuster bolts either. So the rear end is still stock. I'll post a report on my findings once I get a chance to try some of the things posted here.

[Redbird]

So a little 8mm bolt isn't enough to hold the axle in place, but nothing besides friction is going to do the trick better? You tend to know your shit, and I respect your opinion, Pete, but like I said- give it a shot and let me know how it goes.

[JasonW]

:shock: If you don't snug up the adjusters, your bike will fall over to the right. :poke:

I'm with Tim on this one. The pressure required to "pinch" the wheel in place to keep it from moving would demolish the wheel bearings in a hurry. The adjusters do come into play in this as I've seen it firsthand.

It all works as a system.

[Pete in PA]

Well....I geuss we'll have to agree to disagree on this. :roll:

[Redbird]

What's with the eyeroll? :?

I can't prove you wrong from 700 miles away, but I'll still invite you or anyone else to ajust their chain, torque the axle to spec and then turn the ajusters in so they are not holding the axle back at all. Your chain slack and rear alignment will go to shit, quicklike. This is not my opinion or a guess, I've seen it firsthand.

[FiXXation]

The 8 mm rear axle adjusting bolt's threaded shaft size is more equivalent to a standard 12 mm bolt, such as the 16 ft-lb torque pinch bolts used on the front axle. The 8 mm hex head size along with the enlarged ring inside the adjuster, is to accommodate it's installation into the adjuster bracket, allowing the snap ring to do the job the head would on a standard 12 mm bolt. The interior enlarged ring is what would take the "snugging" pressure being discussed here.

I noted very early after getting my bike, that even though the rear axle nut is torqued to the prescribed 69 ft-lb setting, the axle bolt can fairly easily be turned with no backup on the nut. My chain slack also seemed to increase quickly, even though I was not using anywhere near max horsepower on the thing. Resetting the chain slack also put me back to previous settings on the wear indicators.

"Snugging" the adjuster bolts to hold the adjusters back against the chain pressure using just a screw driver type handriver for torque completely stopped my chain slack creep.

The snugging pressure taken by the adjusting bolts will happen to them anyway if the axle slips forward until it can't move the adjusters any further forward.

[bonox]

fuck, pressed back and lost the reply. Short answer:

1. plates inside swingarm stop swingarm rails being crushed when you torque the axle nut. Friction between these plates and the rails is what stops the axle and wheel moving.

2. if you can turn the axle when torqued to the correct value, you have inadvisedly greased every adjuster plate, washer and rail face from not to nut or more likely, your torque wrench is borked or your have stripped the nut (do you still have the vibration resistant washer in the nut btw, or a split pin for castle nuts?)

3. The wheel bearings require preload, and this is mostly what the high torque is for. Under maximum lateral load (when you barrel into a corner) the inside bearing should not go sleck or unloaded meaning that only the outer bearing is taking the load. There is some hard to understand force physics here, but if you apply a (pre)load on a bearing in one direction and then put a load on it in the other direction, as it 'unloads' it is taking part of the force applied to it. This is what happens to the inside bearing on your wheel. If you overtorque the axle, you can put flat spots on the balls (called brinelling) that destroys the case hardening and fooks em really quickly.

Radial preload comes from the factory, and is the reason the two races of the bearing don't slop about around the balls/rollers if you turn em by hand.

4. The adjuster plates are thing, square edged pieces of poor quality material that are only there to allow unloaded relative adjustment of the two blocks within the swingarm rails. If all load were taken on these, the 8mm bolt would NOT fail first - the adjuster plates would straighten out and then the little snap ring would fail. For those of you thinking that playing with these fixes the problem, you are either very very close to the correct load on the axle, but not quite, or you are realising a placebo effect.

Please note that when you put this stuff together, the torques are given for dry threads, and the axles should not be greased (too much) i put a trace on it to inhibit corrosion, but the axle should not be allowed to spin in the bearings inside race - the bearing is there to take this load, not the axle/brg interface. Axle is soft, bearing is hardened - take a guess as to what happens?