Topic: Chain keeps slacking

[tennesseebreeze]

I don't know if this is a question or just a rant, but on my 78 cb400 twin that I use as a commuter my chain goes slack every time I ride. The chain is an o-ring type that has been on for less than 8 months and less than 4000 miles. It don't remember the brand- it wasn't cheap, but wasn't high end either. I've replaced 2 rear sprockets because once it goes slack, it doesn't take long for it to chew them up. I keep the axle and the chain tensioners tight, and it keeps loosening. Is there something I'm not considering? Or is the chain just stretching? Seems like a hell of a lot of stretch to have to adjust it every time.

[Duke McDukiedook]

Are you checking the slack with you sitting on it off the center stand?

[calj737]

Sounds as though the stop nuts in the adjusters isn't present. If you loosen the axle nut, position the tensioner to proper chain deflection, then tighten axle nut, it should stay. For it to "slacken" every time you ride, then either you're not tightening the axle nut or the adjuster is not holding.

[Duke McDukiedook]

yeah, pics of your tension adjusters and axle nut would help.

[flybox1]

Slacker! 
With an axle properly torqued AND the adjuster lock nuts done up, this should be enough to prevent slacking.

+1 to both of the above.

[tennesseebreeze]

Are you checking the slack with you sitting on it off the center stand?

No, I've been getting off the bike to check. I'll post a picture in a minute.

[tennesseebreeze]

I tighten the crap out of both the axle and the set nut of the tensioning bolt, which are new and hardened stainless. Here's a picture. Could it be a consequence of my crappy rear suspension?

[bjbuchanan]

Tension it with your weight on it. I sit with it on the center stand and awkwardly reach down to feel for the 3/4 up and down. This is how I tension it with no helper. If you were to run that same amount of slack but with no weight on the bike that will prematurely wear the chain.

The reason is that the suspension is more or less where it will truly run on the road.

Now hop off the bike and feel for what the slack is like without weight on the bike. That looser slack is what you can set it to now in the future with no weight on the bike and not have to monkey around with no helper

[Eddie]

in the pic it doesnt look like the proper bolt for the tensioner, could be the threads are not right thus loosening.... should have a hex head not phillips...no ?

[tennesseebreeze]

in the pic it doesnt look like the proper bolt for the tensioner, could be the threads are not right thus loosening.... should have a hex head not phillips...no ?

It's not the original bolts, no. But the threads are right. I replaced them because P.O. had some replacements in there that were wrong and seated crooked. They have the wrong heads, but otherwise are correct.

[Vinhead1957]

When you replace a chain you should do both front and rear sprocket too!

[tennesseebreeze]

When you replace a chain you should do both front and rear sprocket too!

I replaced the rear last night, I'll do the front this weekend. I can't afford to get another chain though. I've spent everything I have on my SOHC build!

[2wheels]

To be sure if the axle is moving or not put a piece of tape and mark the location.
Do this on both sides.

Can you take a picture of the damaged sprocket?

[tennesseebreeze]

To be sure if the axle is moving or not put a piece of tape and mark the location.
Do this on both sides.

Can you take a picture of the damaged sprocket?

Yeah, I can snap one later. It's pretty shredded- the teeth are sharp enough to cut flesh.

[Dave Voss]

If you were to run that same amount of slack but with no weight on the bike that will prematurely wear the chain.

This is a common cause for frequent chain slack.  If the chain is adjusted for the proper amount of slack deflection with no weight on the rear suspension, then it will be way to tight in operation, and so the chain stretches from being over tightened, which occurs faster than the stretch that occurs from normal wear under load from the engine.  Also, an over-tight chain will also pre-maturely wear the sprockets.

If you are curious, you could adjust the chain as you normally have been, ride for a while, check the slack noting how much it increased, then ride for a while longer, and note that the slack stops increasing, as the excess chain tension is relaxed.  It's best to tension the chain correctly in the first place, but this would give you some peace of mind in knowing that the chain isn't constantly stretching, but rather just trying to correct the condition of being too tight.

[tennesseebreeze]

If you were to run that same amount of slack but with no weight on the bike that will prematurely wear the chain.

This is a common cause for frequent chain slack.  If the chain is adjusted for the proper amount of slack deflection with no weight on the rear suspension, then it will be way to tight in operation, and so the chain stretches from being over tightened, which occurs faster than the stretch that occurs from normal wear under load from the engine.  Also, an over-tight chain will also pre-maturely wear the sprockets.

If you are curious, you could adjust the chain as you normally have been, ride for a while, check the slack noting how much it increased, then ride for a while longer, and note that the slack stops increasing, as the excess chain tension is relaxed.  It's best to tension the chain correctly in the first place, but this would give you some peace of mind in knowing that the chain isn't constantly stretching, but rather just trying to correct the condition of being too tight.

Okay, this makes the most sense to me. I have been tensioning the chain while off the bike, as well as adjusting a little on the tight side. So when I get on the bike it stretches the chain. I don't want to stretch the thing further, but I'll readjust and mark the axle position and keep a close eye on it.

[tennesseebreeze]

Also, if weight on the bike causes tension on the chain, then more weight or deflection would stretch it more right? The bike is in need of some new rear shocks, so when I hit a bump, the crappy shocks would compress more, giving more tension to the chain, thereby stretching it more...I guess.

[calj737]

It also appears that the adjuster has the axle very far to the rear of the swing arm, possibly indicating a chain too long. Can you remove a link, move the axle forward toward the front of the swing arm some, and then re torque.

Improper tension, and bad sprockets ruin chains. I'm not sure about the suspension causing chain slack that desperately.

Replace the adjusters with proper goods. This is a critically important piece of safety gear, and candidly, Phillips head screws aren't worth #$%*e when your life could spend on it. Grade 5 or better hex bolts and stop nuts.

[tennesseebreeze]

It also appears that the adjuster has the axle very far to the rear of the swing arm, possibly indicating a chain too long. Can you remove a link, move the axle forward toward the front of the swing arm some, and then re torque.

Improper tension, and bad sprockets ruin chains. I'm not sure about the suspension causing chain slack that desperately.

Replace the adjusters with proper goods. This is a critically important piece of safety gear, and candidly, Phillips head screws aren't worth #$%*e when your life could spend on it. Grade 5 or better hex bolts and stop nuts.

Wasn't always that far back. A chain stretched far enough to remove a link may be a chain stretched too far. I don't know. I could take the chain off and measure its play. Anybody know what the play in a chain is supposed to be? Meaning, when you lay it out on a table, push the chain together, then pull on it, how much travel should there be?