Topic: 1978 CB750k Chain Problem

[Bill K]

I'm the proud new owmer of this 78 750k and I'm very excited to have this bike. I'm new to this so bare with me. I got the bike friday and have been out in the shed / shop messing with it ever since. I've got the bike up on the center stand trying to adjust the chain. When I spin the tire the chain gets tight then loose and kinda "hangs up". The sprockets "look" ok but what do I know. Thanks for any help, I'll post some picture as soon as figure out how.

                                                                                      Thanks Again !!

                                                                                                  Bill       

[Johnie]

Some of those chain links are froze / rusted so they do not move around the sprocket.  Common problem with old chains that have not had the best care over the years.  You can spend a lot of time trying to free it up, but the best solution would be to get a new chain and sprockets.  You certainly do not want that chain to break while riding as it will fly into the crankcase and make a hole you do not want to have to deal with.  Let us know how you come out...

[Bill K]

The chains clean and well lubed. I noticed someone messed with the rear sprocket, the "ears" or retaines around the nuts on the sprocket are bugered up. I kinda like the idea of new chain and sprockets and be done with it. Any chance someone put the wrong sprocket on the bike? What gets me is how the chain gets loose then tight. I've got the tire centered perfect.

[jimz]

Hi,
 Having the same problem with 78'' CB550k. Replaced both sprockets and chain, problem remained. A local mechanic suggested possible worn rear dampers as they are the connection between wheel/hub and rear sprocket. Good luck.

jimz

[Johnie]

Probably start by counting the teeth in the front and rear sprocket to see if it jives with the manual.  Maybe you can figure out if the PO changed those or something.  Also check to see if those sprockets are wearing evenly.  You said the chain is well lubed, but that does not mean that every link is free.  You will have to check it link by link.  Maybe the PO gave it a good lube with a seized link?  I had the problem on one of my Honda's and the sprocket and chain solved my situation.  Good luck with it.

[eldar]

The 78K had a 630 chain with 41T rear and 15t front sprockets.
Generally if there chain goes loose then tight then loose and so forth, it means the chain is worn uneven and while maybe usable, it is best to get a new set up. Now, you can stick with the 630 set up if you want, the chain link count is 88. It will go right on with no issues. You can also go to a 530 size. Worried a 530 will not handle the power, consider that modern rockets use a 520 chain.

If you go with a 530, you will need at least a 108 link chain as 530 likes are smaller. I got a 112 link and took off what I did not need. I did this cause it was cheaper at the time but you also would rather have a chain that you can shorten then one you have to extend. I got an RK chain and jt sprockets if I remember correctly. Got them from  mawonline.com

the set cost me about 120 clams, not too bad. It is an X-ring chain too.