Topic: What causes uneven chain stretching?

[Tugboat]

Replaced my chain & both sprockets last year. I've been pretty good about keeping the chain lubed and adjusted. When I got home yesterday I knew that that it needed to be adjusted but it was REALLY loose. So I loosened the axel bolt, adjusted both sides so that the chain had the requisite 1" of play... but when I spun the wheel around 1/2 turn it was really tight.

I assume that part of the chain is stretched so that as it goes around it's tension is correct/tight/correct/tight etc. Is there anything specifically that can cause this? BTW it was just a regular ol' chain.. not o-ring or x-ring or anything fancy.

[Tugboat]

Bump.... anyone?

[flybox1]

No answer to your stretch issue, but have you tried adjusting it with someone (in similar wt to you) sitting on it?

[cookindaddy]

I can't really see how a chain could wear unevenly. I would look carefully at the mounting of the rear sprocket. Is it running true? If you have a magnetic finger dial micrometer, you could mount it to the frame and use the finger to check for any runout of the rear sprocket. Are the rear bearings ok?

[Bakeoff]

I can't really see how a chain could wear unevenly. I would look carefully at the mounting of the rear sprocket. Is it running true? If you have a magnetic finger dial micrometer, you could mount it to the frame and use the finger to check for any runout of the rear sprocket. Are the rear bearings ok?

^^^^^Nailed it on the head.  You could also have a bent shaft on the front sprocket... 

The only things that would make a chain stretch unevenly are poor quality, or being the guy that downshifts without using the clutch.  That will beat up your cush drive and stretch a chain in no time.

[madmtnmotors]

I think you can get uneven stretch if you overtighten the chain while on the center stand. While riding, if the rear suspension bottoms out (or close to it) with an over tightened chain, I believe you can create an uneven stretch since the swingarm pivot does not line up with the front sprocket (which would be very difficult to do). I've had an unevenly stretched chain in the past and I think it may have been a result of overtensioning the chain, with maybe just half an inch of freeplay (on the centerstand) and then a deep cycling of the rear suspension. I tend to tension the chain on the "loose" side now (about an inch of freeplay while on the centerstand), and haven't seen an uneven stretch since.

[Operator]

Madmtnmotors- Thanks for bringing up this point. I had this issue with my last chain, right before I replaced my rear shocks (old ones would bottom out with all my camping gear loaded). I was running with the standard 1/2 inch of free play. Since I replaced the shocks- no issue. I may also take your advice and go with 1" of free play.

Thanks

[madmtnmotors]

Madmtnmotors- Thanks for bringing up this point. I had this issue with my last chain, right before I replaced my rear shocks (old ones would bottom out with all my camping gear loaded). I was running with the standard 1/2 inch of free play. Since I replaced the shocks- no issue. I may also take your advice and go with 1" of free play.

Thanks

The one inch is kind of subjective, I used to obsess over the 3/4" freeplay described in the manual (CB750K8), to the point that I would err on the "tight" side (making my adjustment closer to 1/2"). Now I tend to err on the loose side, making my adjustment closer to 1". I still have an annoying issue where the master link (clip type) tends to tighten up, i.e. as I turn the rear wheel and the master link comes around, it holds a little "kink" in shape. Seems to be grabbing the adjacent link a little more tightly than the other links do. I've never broken a chain in 40,000 miles so I can't be mucking things up too badly....

[TwoTired]

I assume that part of the chain is stretched so that as it goes around it's tension is correct/tight/correct/tight etc. Is there anything specifically that can cause this? BTW it was just a regular ol' chain.. not o-ring or x-ring or anything fancy.

Causes?
-- inadequate film strength of the lube
-- inadequate distribution of the lube to all the pivot pins.
-- improper adjustment of the chain.  I'll explain:
If the chain is adjusted without weight on the suspension, it can be too tight when the shocks are compressed, which over stresses the chain and causes increased wear during the stress event.
--  By the same means, worn swing arm bearings can change the geometry and intermittently tighten a chain during riding operation.

Cheers,

[Duke McDukiedook]

Could be that your conked chain is binding up on you also if it has some rust and age.

[phil71]

i've had chains with stiff links here and there...never really gave it a 2nd thought..

[Markcb750]

The primary cause of changing tension as it goes around has been jamming of the chain due to worn pins/rollers.  As the chain starts to wear from lack of lubrication/over tightening/ impaction of contaminate a few links will be contaminated worse then the others and will jam instead of bending smoothly as they engage the sprockets.   the problem can be abated temporarily with a very thorough cleaning and re-lubrication, the worse the chain is the quicker the problem will return.


 ALWAYS (yes ALWAYS) replace both sprockets when you replace the chain if you want to get maximum life from a chain. Even a tenth of a mm of wear (0.004") will quickly be transferred from the worn sprockets into the chain. 

If you can check the sprocket alignment should be parallel to each other and within a millimeter or so of aligned.  A taught wire will work, a laser if you know how to align the beam to the sprockets.

I know they draw more power and on some machines cannot be used because if interference problems, but I do not hesitate to recommend an O-ring chain.  it keeps the pin/roller sealed from outside contamination and will run smoother/longer with minimal maintenance. Particularly effective in dusty environments.  You still must clean the O-ring chain well with WD40 or similar, wipe ti down till dry and let the cleaner flash off, then use a good minimal fling lubricant.  This lube application is primarily for the leaf surfaces as the O-rings prevent new lubricant from entering the pin/roller area. 

Just to brag a little...My Diamond Nickle plated O-ring chain has 8000 miles and has stretched/worn less then 1 notch on the alignment marks. 

[phil71]

do people still clean chains out in kerosene?
I seem to remember old timers doing that.

[Markcb750]

do people still clean chains out in kerosene?
I seem to remember old timers doing that.

WD40 is pretty much "kerosene"... a light petroleum solvent with some "magic" herbs and spices...

[SanDogDewey]

I read that if you have an even number of teeth on both sprockets, you will get uneven chain stretch. You should always have an odd number of total teeth. The concept being that with an even number,  the same links are always hitting the same sprocket teeth, and with an odd number the links walk around the sprockets. Truth or wife's tale?

[Deltarider]

ALWAYS (yes ALWAYS) replace both sprockets when you replace the chain if you want to get maximum life from a chain.

I've always done two chains on one set of sprockets (learned from Honda mechanics who did the same with their 500's). And why not, it's the pitch that matters. Most cost effective solution for the CB 500 anyway.
BTW, never had a chain that wouldn't wear unevenly.
Honda's recommendation for free play in the Owners Manual is to stif IMO.

[Markcb750]

ALWAYS (yes ALWAYS) replace both sprockets when you replace the chain if you want to get maximum life from a chain.

I've always done two chains on one set of sprockets (learned from Honda mechanics who did the same with their 500's). And why not, it's the pitch that matters. Most cost effective solution for the CB 500 anyway.
BTW, never had a chain that wouldn't wear unevenly.
Honda's recommendation for free play in the Owners Manual is to stif IMO.

When I had a 500 Four in 1972/3/4 I went through chains every 4 to 5 thousand miles. despite once a week cleaning and lubrication.  I only changed the sprockets once at about 16000 miles.  At the time I believed the problem was Arizona desert dust.  But who knows; I could have been setting the tension too "stiff".

I don't know how to decide if a chain is worn unevenly or is binding because of impacted debris without dis-assembly and analysis of each pitch. By the experience of cleaning a binding chain and having it run smoothy for some period of time I believe my chains wear relatively evenly or they would not improve by cleaning. 


FWIW: Even numbers of teeth will result in the them regularly engaging the same teeth.  I know this can introduce a wear problem in gears and should be avoided by the designer.  Unencumbered by the thought process I would say it must be true for chain drives because all my Hondas have uneven tooth totals.

[sportsvan]

  have the same problem on my 900FA. the existing chain was worn & had a tight spot so last week i fitted a new chain (no sprockets as they looked ok)  thought the problem was solved, but after checking it after a ride it already has a tight spot. arghhhh.
it must be what has already been suggested. either sprockets not 100% or hopefully not, problems with the gearbox final drive output shaft..
the sun is out in England today !