Author Topic: Marks on crankshaft  (Read 1773 times)

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Offline mazingerzeca

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Marks on crankshaft
« on: August 27, 2009, 01:34:38 AM »
Hello all.
The bike is a CB750 K7
I took the crankshaft to the machine shop to have it measured. The guy told me that one of the big end journals was scored, and yes, you could feel the marks with your nails.
The guy told me that it can be solved putting a 0,25 mm oversize shell and removing 0,25 mm from the crankshaft journal. He told me that they don't have that kind of shells for bikes.
Where can I buy oversize shells for this bike?
Thank you.

Offline bryanj

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Re: Marks on crankshaft
« Reply #1 on: August 27, 2009, 06:03:27 AM »
You can't
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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Offline mazingerzeca

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Re: Marks on crankshaft
« Reply #2 on: August 27, 2009, 06:52:19 AM »
So, how can I repair these marks? Are they unrepairable? Should I just leave them on the journal and buy new standard shells?

Offline 754

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Re: Marks on crankshaft
« Reply #3 on: August 27, 2009, 07:47:47 AM »
Actually someone posted that they are now selling some on ebay
(dont know how well made they are)

Used cranks are fairly reasonable still, and probably cheaper than grinding your old one and buying them bearings.

 I would be fairly worried aboyut WHY it did, and be carefull what oil you run.
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Offline MCRider

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Re: Marks on crankshaft
« Reply #4 on: August 27, 2009, 07:50:41 AM »
Actually someone posted that they are now selling some on ebay
(dont know how well made they are)

Used cranks are fairly reasonable still, and probably cheaper than grinding your old one and buying them bearings.

 I would be fairly worried aboyut WHY it did, and be carefull what oil you run.

I have a good used one for sale, but I think the shipping to Spain is a deal breaker. Maybe not?
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Offline mazingerzeca

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Re: Marks on crankshaft
« Reply #5 on: August 27, 2009, 10:09:52 AM »
McRider, sent you a PM

Offline Big Jay

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Re: Marks on crankshaft
« Reply #6 on: August 28, 2009, 04:48:18 PM »
I answered your e-mail on this.

Jay

Offline AshimotoK0

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Re: Marks on crankshaft
« Reply #7 on: August 29, 2009, 04:55:48 AM »
I posted this about the undersize shells but I am not sure how deep the nitride hardening is to allow this.

Good used cranks are mega cheap in the US but the shipping to Europe can be $150-200

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Offline mazingerzeca

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Re: Marks on crankshaft
« Reply #8 on: August 29, 2009, 05:29:19 AM »
Thanks for your help.
I have a line on a used crankshaft. The shipping costs will be high, but it will be the only way to obtain one. Difficult in Europe, specially in Spain, where this bike was not sold.

Offline bryanj

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Re: Marks on crankshaft
« Reply #9 on: August 30, 2009, 05:34:01 AM »
If its cheaper from UK i think i have a couple in crankcases that can be split
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!