As I near the completion of my first full rebuild, I'm left with a question...
Old cranks, are they junk or can anything be salvaged from them? I'm going to end up with two and seeing as I'm getting into this re-build lark it'd be silly to bin them if I can send them to Dave and he can make em good?
It all depends on if the pin is good or bad. If its bad I would say just scrap them since enough of us have many of these laying around for many years to come if ever its decided to replace pins or stroke them. If the pin is good that crank is much preferred over the new style because it is much better balanced and probably stronger. If used in a new case it does require stator or case mod to stator mounts though since the flywheel is closer using the old cranks. I wish all my motors had old style cranks though.
This is an easy one. if the crank was run to destruction where the rod itself is discolored from heat then the crank is junk. If the rod is discolored then the crank web surface will have developed micro cracks from the heat. You would not want to use this crank for a repin or stroker. If the rod is not discolored but only locked up then the crank halves should be reusable. This is also why it has always been very important to update the cranks before they go bad.
You have to split the crank to really know but like wistech said you can tell by looking at it in most cases. Especially if its locked up tons of play or massivly discolored.
My guess is you just have run into the really unbalanced cranks which is why you felt vibration. I would say from looking at it is a good chance all it needs is Z400 bearing and balance. Never know until its split. To do that you need a plate and a press or I do it for $10 and shipping.
You will need a VERY thick steel plate jig made in order to press the crank halves. I mean like a one inch thick plate with tapped holes so you can tightly secure the crank as there is massive pressure needed to press them apart.
