Dave,
sounds to me like the metal clutch arm is being loaded in a manner for which
it wasn't designed, causing the failure in the wrong mode, just like you
expressed. I would hazard a guess to say that the fork is being loaded on
only one tang because, when mounted, it is no longer
parallel/normal/correctly positioned to the pressure plate surface when it
sweeps thru its arc. Your shifting gets worse because the fork is yielding.
The 'adjustment' you describe (that seems now to be an indicator of
on-coming breakage) is that one ear (tine?) on the fork yielding, so now the
second tine contacts, but the first one has yielded, overtime the second
gets overloaded, and BANG!
Since the tranny case is aluminum, when it is out you need to check if the
clutch fork pivot is seated in the aluminum or if there is a bushing. (I'd
bet someone can answer this before you pull it out?) Check to make sure the
hole is not ovaled and the bushing is square as it should be.
The other thing to make sure is that when you increase the throw of the
slave, the backside of the fork isn't contacting something, putting the fork
in a bending load. You could conceivably wear the fork down by rubbing on
something and then break it.
Just conjecture, but at least it is roadster related.
Fergus O, 69 2000, HB, CA
<< About a month ago, I had solved a clutch hydraulic system problem
by increasing the "throw" of the slave cylinder. This was needed
because wear of the linkage prevented proper adjustment of the
clutch clearance. Since I did this, my shifting performance has
been so very much better than it had been in a long time.
Although the clutch failure occurred only a short time after I
made the change to the slave cylinder throw, I can't think of any
way that change could have been the cause of the failure. >>
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