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Discussion Starter #1
Hello Gurus,

Cracked open an old Suzuki sled engine and thought I had found the problem with it. Overheated crank pins as visible here
IMG_0992.JPG

Then a closer look showed no such discoloration on the needles. ¨Could´ve rubbed off¨ I thought.

Next, once the crank was out, a better look overall showed not only the exact same discoloration around both crank pins but none on the pins themselves.
Furthermore, the heat coloration extends around the actual shaft, on both ends, and only there. The rest of the webs and shafts are fine.

IMG_1000.JPG

IMG_1002.JPG

So, looks like the holes for the pins are heated for assembly, but that leaves out the coloring around the shaft.
So, are the shafts ground to final size and overheated in the process? The discoloration from around the pins appears to have taken place after the one around the shaft.
Bearings from either side show no heating marks at all.

I had never seen this before. Can someone explain, please?
 

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Discussion Starter #3
Hi Flotek, thanks for responding.

No play that I can detect. Neither axial nor radial. Certainly nothing undue, and definitely none at all between crank webs and pins.
There are no signs of heat on the pins, hence my thinking the heating must've happened before assembly.
The neat ring of heat discoloration around the pins makes me think of inductive heating for assembly. Only a small area affected.
 

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Discussion Starter #5
Yes, all seems fine, just hadn't seen such discoloration on a crank before.
I intend to run it, but need to put some work into it first since I'm turning this in line twin into a boxer engine.
Thought I'd check before getting deeper into the process.

Many thanks
 

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That discoloration is from assembly at the Suzuki factory, it makes it a a lot easier to press the crankshaft together. There is nothing to worry about. Measure side to side clearance and check for rod play up and down and try rock the rod, if it checks out then run it.
 
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