Author Topic: wacky chain (Read 7924 times)

dieselbenz · « **on:** July 25, 2005, 04:21:16 PM »

Yes, I know, the obvious answer is "change the chain and sprockets." I will do that (probably next year). This is more of a theoretical how-come sort of question.

1977 CB-500K. With the bike on the center stand and spinning the rear wheel by hand, there is a good 1" difference in chain slack at different data points as the chain rotates thru 360 degrees. Too lose at one point and then only marginal slack at another. I tied a piece of twine to one of the links to mark the "tight" spot and it always occurs at the same place. I have checked each and every link to make sure none are binding, so that isn't the problem. I've not knowingly done anything that might have deformed or bent one of the sprockets.

Anyone been here and can shed some light on this? I am really waking up at night trying to do some theoretical troubleshooting but am coming up empty.

There is no unusual noise running down the road that suggests the chain is binding. Just a slight bit of chain slap as I downshift when slowing down, but nothing objectionable.

I should add that, like one of the current threads, I am running four-into-one exhaust and have welded a piece of round stock to the left side of the center stand to keep it from rotating up into the chain path, but I can't see how that would have anything to do with this issue.

Don
Iowa

eldar · « **Reply #1 on:** July 25, 2005, 04:29:58 PM »

Gee about the only thing I can think of is that the chain has stretched more in one area than another. Say for instance, the bike was sitting for a while. The top part of the chain has more tension since when it was parked, the front sprocket pulled a bit on the chain and was left like that. The bottom section did not have this. This may cause one area to stretch more than the other.

Killer Canary · « **Reply #2 on:** July 25, 2005, 04:42:52 PM »

Drive chains always wear unevenly,sooner or later. Sometimes a little more schlock accumulates in some valleys between teeth than others, forcing alittle more stretch in that spot.Poorly made(cheap) sprockets will cause uneven tension when brand new.

Buffo · « **Reply #3 on:** July 25, 2005, 05:26:05 PM »

in the area of the slack, test the play in the links by pushing and pulling 2 links at a time .Where an inner link is rivited to an outer link. Do this all thruogh the slack. one rivit at a time. then check the side of the chain that seems to have less slack. the side with less slack should not have as much free play inbetween links.

It is best to do this with the chain off the bike so all the tension is off of the links.

A little info: If your chain brakes at high speed or under acceleration you have a good chance of doing ALOT of damage to your bike. The chain could crack the case or worse slap a hole in your case. Broken chains are serious business.

Even a real good chain is only $130.00

Don

dieselbenz · « **Reply #4 on:** July 25, 2005, 05:46:55 PM »

Is this a chain in danger of breaking? I'd like to finish this riding season (remember, I am in Iowa!) before replacing chain and sprockets. But having survived one should-have-been-fatal bike crash I don't want to see just how good my Shoei helmet really is.

eldar · « **Reply #5 on:** July 25, 2005, 06:06:06 PM »

well gee in iowa, I would ride till the snow flies! Inspect your chain, if it goes past a certain marker on your bike, replace it. Since you say it goes past 1 inch in slack difference, you may want to replace it. Check your sprockets and replace if needed. They do not need to be replaced as a group unless you have really cheap sprockets. Of course this depends on how many miles you have on the chain and sprockets.

dieselbenz · « **Reply #6 on:** July 25, 2005, 06:24:32 PM »

Odometer has only 11K on it. I don't THINK it has turned over but 11K for a 1972 would be pretty low miles. I do know that the original owner just used the bike to ride too and from his farm (10 miles north) occasionally so 111K is unlikely. I think sprockets and chain are probably factory original.

eldar · « **Reply #7 on:** July 25, 2005, 08:00:32 PM »

Ok now if these are still factory parts, GET NEW CHAIN AND SPROCKETS!! Anything that old will be very dangerous from metal fatigue. I would not even ride with old parts like this. Spend about $100 - 120 for all 3 parts.

dieselbenz · « **Reply #8 on:** July 25, 2005, 08:20:42 PM »

I don't know that they are original, just guessing. The previous owner was a maintenance nut (farmer). But I agree, I should replace the entire thing.

TwoTired · « **Reply #9 on:** July 25, 2005, 10:47:37 PM »

Quote from: dieselbenz on July 25, 2005, 06:24:32 PM

Odometer has only 11K on it. I don't THINK it has turned over but 11K for a 1972 would be pretty low miles. I do know that the original owner just used the bike to ride too and from his farm (10 miles north) occasionally so 111K is unlikely. I think sprockets and chain are probably factory original.

It is not uncommon for a non-o-ring chain to wear unevenly. (no, don't put an o-ring chain on it). Uneven lubrication or a concentration of dirt in the right (wrong) places can cause wear in specific areas. It is unimaginable that the original Cb550 chain could last 111K miles. With only 11K miles, the existing sprockets are likely still good if they have had decent lubrication. However, the smaller front one does wear faster than the rear sprocket. Having said that, a chain with tight spots also has uneven link spacing that can wear both sprockets at an accelerated rate. It is best to examine the sprockets to see if they need replacing. There is very little flexing of these sprockets, so metal fatigue is of very little concern, if any. Tight spots or uneven wear in the chain is cause for immediate replacement. Sprocket replacement decisions are made based on physical wear limits. Or, how fast that money is burning a hole in your pocket.
Cheers,

LRODMAN · « **Reply #10 on:** August 05, 2005, 05:10:30 PM »

Don,
I did some normal maintaince this week and found that I could not adjust my chain out any further with the adjusters. It became stretched with time. I also noticed that the chain went from too tight to too loose when rotating the rear wheel. I replaced the chain with a new oring this afternoon and what a difference! Execleration, shifting and crusing are all much smoother. Your chain is definately your problem. Don't wait to replace yours. A worn chain is unsafe and places undue stress and wear on already old parts. As for your sprockets a visual check for wear should tell you what to do. Make sure you get the right number of links and a tensile rating in excess of 9,000 lb for a 750.
Larry

eldar · « **Reply #11 on:** August 05, 2005, 05:17:28 PM »

look in your owners manual if you still have it. It will tell you what chain your bike came with. At least mine does. I have a 78k and it came with an o-ring chain. Currently I dont have the money to get an oring chain so I got a standard one which will work just fine for at least a year.

kghost · « **Reply #12 on:** August 05, 2005, 07:11:42 PM »

Uumm.......

Guys? Metal fatigue is a function of cycles not age. Its how many times it stretchs not how old it is.

eldar · « **Reply #13 on:** August 05, 2005, 07:26:00 PM »

metal does fatigue though over time even if the only force on it is gravity. It is not a big concern these days but back when it could be.

Buffo · « **Reply #14 on:** August 05, 2005, 07:30:58 PM »

That chain is junk. Save yourself a lot of time and heartache and spend the 100. - 130. and buy a new one.

Don

kghost · « **Reply #15 on:** August 05, 2005, 08:02:07 PM »

Eldar, Are you postulating that the chain fatigued just hanging there for 20 odd years?

dpen · « **Reply #16 on:** August 06, 2005, 07:05:42 AM »

Replace the sprockets too.
A new chain with old sprockets will root the chain quickly.

eldar · « **Reply #17 on:** August 06, 2005, 07:34:36 AM »

Yup. You dont have to be using something for it to fatigue. Gravity will do it just fine if left long enough.

kghost · « **Reply #18 on:** August 06, 2005, 08:34:45 AM »

And the scientific basis for that fatigue is?

eldar · « **Reply #19 on:** August 07, 2005, 11:02:17 AM »

Well here is a link on some of the subject. it is hard to find since the first 3 pages are all about a game.
http://print.google.com/print?id=wlHwTcO68iYC&dq=metal+fatigue&oi=print&pg=PA1&sig=zZnzYab4cAleStNyDC08IbJap-E&prev=http://www.google.com/search%3Fq%3Dmetal%2Bfatigue%26sourceid%3Dmozilla-search%26start%3D0%26start%3D0%26ie%3Dutf-8%26oe%3Dutf-8%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official

Fatigue happens whenever a load is placed on something and even gravity places a load since the material has to hold is own weight.

kghost · « **Reply #20 on:** August 07, 2005, 12:52:03 PM »

So it would reach failure point in what about 4 million years?

eldar · « **Reply #21 on:** August 07, 2005, 01:00:43 PM »

depends on the material. Remember, chains are better now than they were back then. The steel is stronger and more resistant to fatigue. In short, while fatigue is not that much of a problem now, the chain that was in question may have been original or from the 70s and not as good of quality. Thus it would fatigue more just from gravity. Look at an old truck and see how the frame sags. Trucks these days do not suffer from that hardly. It is an age an quality thing.

kghost · « **Reply #22 on:** August 07, 2005, 01:15:23 PM »

Sorry Buddy, Bull#$%* says I.

The springs sag on old trucks because of weight and usage. Weight of the truck not the springs. (yes I realize weight is a function of gravity but remove the truck weight from the springs and don't bend them - the SOB's will last till the next two centurys)

When I went to engineering school, Fatigue was defined as being caused by an outside influence.
Trying to say that the chain will fatigue by only hanging on the sprocket due to gravity gave my engineer friends a good laugh.

78_SaltLick · « **Reply #23 on:** August 07, 2005, 02:06:52 PM »

Well im in the same basket. How in the world do we know what size or type of chain to order? Yet another basic, stupid question i know. I have a 78 CB750K ( i just post pics of it yesterday, if you guys havent seen it yet) seen one....seen them all? ha ha.

dieselbenz · « **Reply #24 on:** August 07, 2005, 03:31:37 PM »

Dennis Kirk web site (www. denniskirk.com, I think) takes you through menus to get the right part. If that fails, you can call them.

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Author Topic: wacky chain (Read 7924 times)

dieselbenz

eldar

Buffo

dieselbenz

eldar

dieselbenz

eldar

dieselbenz

LRODMAN

eldar

eldar

Buffo

eldar

eldar

eldar

dieselbenz