Had another try at diagnosing the problem today... Pulled off the chain to isolate the shaft only, in case any issue with cogs, but problem remains. With the rear jacked up and pedal pushed forward just enough to see crack of light between right plate and cone (ensuring it makes no contact with cone to rule out any movement of the cone/pulley/clutch arm assembly), I can visibly see the gap grow/shrink very slightly on each rotation. And also same deal between left plate and cone.
So I have to assume the shaft/plates are not rotating perfectly true which is what's causing the shuddering issue... Only it's odd that it only shudders when driving forward, not in reverse.
But having already gotten shaft replaced, bearings replaced, and plates professionally machined... I'm still at a loss at what else could be causing this? Is it possible the plates are slightly wonky? Or something else I'm completely missing?
