'76 3CL Ceriani's - lack of stroke problem

[Laverdaton]

Can anyone explain this........

History: When I removed the front wheel on my bike I had one hell of a job tapping out the spindle. The problem was caused by one of the fork legs exerting all it's spring pressure downwards, preventing the spindle from being removed.

Present: Today, I replaced the fork seals in both legs. I noticed in one leg that the inner steel tube (the one that the bottom allen screw locates into to the hold the whole fork together) was free to slide up and down within the stanchion and I could remove it by inverting and tapping the stanchion on the bench. But, the other steel tube on the other leg was firm and appeared fixed.

Solution: Not knowing which of the two legs was working correctly, but definately suspicous of the leg with the stuck tube, I stripped out all of it's internals. To remove this inner tube (which is an assembly consisting of the tube and an aluminium sliding bush-25mm long- all held together with a circlip) I had to tap it out with a very long wooden drift.

conclusion: I measured the ali' bush diameter which is 0.1mm bigger than the one on the other leg. I've checked and double checked - there is no way that this bush will slide in the stanchion. Yet if I use the other bush, it'll slide freely!! My chrome stanchion doesn't look bent and doesn't have any 'dings'. I don't have a surface plate to check for straightness so used the kitchen worktop!! - as I said it looks straight.

Am I missing something here?..........

 

[Tippie]

I had the same thing with my ?74 Cerianis regarding the aluminium spacer. It was marginally larger od than the other side and was a bastard to get out of the leg so obviously not exactly precision machining from new. I spun a scrap off it in the lathe. They should be a hand assemble part, not require force either in or out. Check that you don?t have a burr from the circlip tearing into the aluminium part as it is removed. The damper rod (which is bolted to the bottom of the slider must be free to slide up and down through both the aluminium part mentioned, all the damping valving and the steel stanchion. You have to find out which part is doing the binding and why. This is easily done part by part as you have it disassembled. Check for a dinged/bent lower fork-leg or damper rod. I found a Duc once with different length damper rods in the forks!

 

[jotacorsa]

the bushes pick up crap from dirty fork oil leaving ridges in the bush and the leg
if you look at the bush you'll likely see a lot of vertical scoring that need the edges made smooth
you may be measuring from the top of the ridges form the scoring

likewise in the tube you'll see corresponding vertical scoring
you'll want to give them a hone

the bush should drop through, lightly oiled, of its own weight much like a tappet in an iron bore

 

[RUSS]

Interesting thread.
I left my 77 3cl in the shed and went sailing for 10 years.
The forks were in perfect condition when I left and well maintained.
When I returned, the forks were not returning after being compressed.
I striped them and found the alloy piston or bush, to be binding in the tube.
There were no scores, burrs, dints etc.
I lapped them down with fine wet or dry sand paper and kerosene so they were a tight fit but no longer binding.
The forks had done 50,000km before binding! It seems the alloy pistons swelled!!!
Doesn't sound right to me but they are working well again.
None of this probably helps but you are not alone.
Russ