Crankshaft repair

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green thumbs
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Crankshaft repair

Postby green thumbs » Tue Sep 12, 2017 5:43 pm

A choice between a bent crankshaft and one with some rust/pitted bearing journals has led to
a emery paper and oil in an attempt to salvage a workable crankshaft.
Am I wasting my time? Any suggestions?
I have feelers out for a better crankshaft too.
Crankcase is plain bearing connecting rods are needle bearing...long story we need not get into here...save that those are only option..
Louis

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Buccaneer
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Re: Crankshaft repair

Postby Buccaneer » Tue Sep 12, 2017 6:53 pm

People / machine shops used to straighten crankshafts.
Not sure if anyone does anymore or not.

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Richard A. White
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Re: Crankshaft repair

Postby Richard A. White » Tue Sep 12, 2017 6:58 pm

If you have access to a good welder meaning the person, he can fill in those pits, then take it to a Professional Automotive machine shop. They will have the correct equipment to regrind it back down. I had my Caille Single crank reground, cost $60...well worth it

Richard A. White
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Chris_P
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Re: Crankshaft repair

Postby Chris_P » Tue Sep 12, 2017 6:58 pm

I have NEVER been able to polish out a crank that had pitted/rusted journals. Within spec anyways to where I was happy with it. If you can see the outlines of the needles, by the time you polish it out, you will be out of spec.

I suppose this all depends on how rare the crank is? If we are talking about a rare crank, attempting a repair may be your only option. If you are talking a 50s OMC Big Twin, don't waste your time, there are gazillions of them out there to replace it with.

green thumbs
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Re: Crankshaft repair

Postby green thumbs » Tue Sep 12, 2017 8:38 pm

Thank one and all for your input. Not a rare crankshaft, just don't have a better one handy.
Will ramp up search for a good to go replacement.
Louis

BillW
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Re: Crankshaft repair

Postby BillW » Wed Sep 13, 2017 5:51 am

Just my observations from over the years: Pits in the crank where plain bearings ride are usually not a problem if the crank is simply cleaned up enough to remove any high spots of rust. Pits where needle bearings run can be okay as long as you can't catch a fingernail in them or if they're not across more than half the width of the surface. It WILL make for a noisier engine, though.

Getting a machinist to do anything around here can be absurdly expensive. I just had to pay $80 to have two slots put in a shaft for a pair of 3/4" woodruff keys. He is the only guy on Cape Cod that would even DO it.

fleetwin
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Re: Crankshaft repair

Postby fleetwin » Wed Sep 13, 2017 11:42 am

What engine is this? Can you post some pictures? I guess a lot depends on how much you will be using the engine afterwards as well...
I agree with Bill, plain bearing/bushings are less effected than roller/needle surfaces. I would be hesitant to trust just any machinist to do crank repairs, look for a replacement crank if needed.

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Re: Crankshaft repair

Postby Buccaneer » Wed Sep 13, 2017 4:57 pm

From the Johnson 3rd Edition manual.....
Attachments
crank straightening.png
crank straightening.png (300.83 KiB) Viewed 127 times

green thumbs
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Re: Crankshaft repair

Postby green thumbs » Wed Sep 13, 2017 6:00 pm

That looks like a pretty heavy duty holding device.
If that base is a slab of solid metal it might not be very portable
Thanks for the photo and instructions.
Louis


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