What to do if my forks are...forked?

[SenseAmidMadness]

I suspect the front forks in my 1980 CB750K might be worn out.

These are replacement forks -- one of the originals was so rusty it got tossed out, and the replacement single fork made for a lot of stiction so I replaced them both with a matched set from another bike. Ebay set, no rust in the area the fork moves around, but some odd vertical wear patterns in the chrome.

I'm still getting stiction, and the inner surface of both fork lowers doesn't look very smooth. Lots of what look like shallow scratches and wear spots.

With new fork seals, even lubed with fork oil, the fork lowers will not slide down the chrome tubes by gravity alone when mounted to the bike.


Is there anything I can do to internally smooth out the lowers and make these forks less sticky when moving, or do I need yet another set of forks?

 

[Bo82CB]

Your outer fork tubes slide inside bushings mounted inside the lowers. Outer tubes should not come in touch with lovers!
Are your outer tubes straight!? if you have static wheel balancer, put tubes on there and check for runout.

 

[SenseAmidMadness]

This is where it gets weird. There appear to be no bushings mounted in the lowers or to the upper chrome tubes. Just bare aluminum and chromed steel. Maybe a touch of deposited bronze or copper alloy on the lowest tips of the chrome tubes but no bushing piece.

I have rebuilt forks where those bushings, typically moly-coated bronze, are inserted just below the fork seals or snap onto the chrome upper tubes. These forks have neither of those.

Really don't think they are bent but I will check. I suspect I need to order another set of forks, just to compare parts...

 

[SenseAmidMadness]

Your outer fork tubes slide inside bushings mounted inside the lowers. Outer tubes should not come in touch with lovers!
Are your outer tubes straight!? if you have static wheel balancer, put tubes on there and check for runout.

I checked the parts diagrams -- it turns out that from 1981 onwards the CB750K had those bushings. 1980 and before it was just the chrome tubes sliding inside the aluminum lowers, no bronze between them at all. Not exactly a long-lasting design!

I ordered a set of 1982 forks on Ebay and will see if those improve the suspension at all. In theory they should be a lot better...