Author Topic: Pitted journal and bearing  (Read 1568 times)

Offline sgd37

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Pitted journal and bearing
« on: December 30, 2016, 05:31:59 PM »
Merry holidays to all :)

I've been slowly getting ready to reassemble my engine, but the more you look the more you see. So I noticed this pit (possibly due to corrosion) on the #4 rod journal which snags on my nail.
http://imgur.com/VzE6OWN
Is the crank still usable since I know you can't grind them on a cb500? Should I polish it?

Second there is a pit on the big end bearing of #3 rod which doesn't snag but can be felt with a finger.
http://imgur.com/f7LaYoo
Does it need replacing? and if so do both half shells need to be replaced?

Thanks for your help

Offline Bryanj

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Re: Pitted journal and bearing
« Reply #1 on: December 30, 2016, 05:35:50 PM »
For peace of mind I would fit a replacement crank with shells, for a low use bike not used hard they may well both work for quite a while

Offline Trigger

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Re: Pitted journal and bearing
« Reply #2 on: December 30, 2016, 05:39:52 PM »
I would get the journal metal sprayed, then ground to STD and fit new shells.

Offline MCTID

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Re: Pitted journal and bearing
« Reply #3 on: December 30, 2016, 07:38:57 PM »
Trigger.....any recommendations for a Company who can Metal Spray and Regrind Cranks (I have some Triumph Twin cranks I want to reclaim).
Cheers.
Now: 2008 CB1300S, CB750K4, 1970 Bonneville. Various other 1960's 650 Triumph T120's/ TR6's/ TR6C's (all in bits...many, many bits unfortunately). Previous: 2007 CB600FA, 1976 CB500 Four. BMW F800ST. GS750E. ZZR1100. CB1300 (2). ZXR1200S. VFR800. CB750 Nighthawk. CX500. XS500 Yam. Suzuki GT500. BSA A10. Various Lambrettas. Zundapp Bella (honest).

Offline sgd37

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Re: Pitted journal and bearing
« Reply #4 on: December 30, 2016, 08:01:13 PM »
Thanks for the reply.

From my own research people have run knicked cranks after polishing. Would this not be a similar situation. Could this lead to engine failure?

Cheers

Offline Trigger

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Re: Pitted journal and bearing
« Reply #5 on: December 30, 2016, 11:16:12 PM »
Trigger.....any recommendations for a Company who can Metal Spray and Regrind Cranks (I have some Triumph Twin cranks I want to reclaim).
Cheers.

I would use T&L at Bedford. If you phone, wait for Derick's extension number to come up. He is the Brit engineer at T&L  ;)

Offline kevski

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Re: Pitted journal and bearing
« Reply #6 on: December 31, 2016, 11:39:16 AM »
They look like corrosion marks, if the snag on the rod journal is not a raised one just give it a light polish to take off any sharp edges, and the bearings i would replace, though you could run with that for years oil will fill these while running, it won't lead to engine failure as the damage is very slight and i assume you will not be running flat out for prolonged periods anyway.
« Last Edit: December 31, 2016, 11:46:39 AM by kevski »

Offline sgd37

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Re: Pitted journal and bearing
« Reply #7 on: January 04, 2017, 05:10:19 PM »
Cheers for the reply and happy new year.

When it comes to polishing could I use the strip of 600 grit and shoelace technique?

Offline matthewmosse

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Re: Pitted journal and bearing
« Reply #8 on: January 04, 2017, 06:56:20 PM »
If it does prove rough, I think I have a few spare cranks that could be dug out and checked. Are 500 and 550 cranks the same?
Got a 500/4 with rust and a sidecar and loadsa bits. nice and original and been round the clock

Offline Bryanj

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Re: Pitted journal and bearing
« Reply #9 on: January 05, 2017, 07:39:44 AM »
Yes matt all the cranks are the same (except 650 before somebody shouts) As to the polishing crocus paper with oil

Offline kevski

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Re: Pitted journal and bearing
« Reply #10 on: January 05, 2017, 09:31:51 AM »
At least 1200 grade, i have a 1200 grade mesh that i use for things like that, i got it when i was a plating tech.

Offline Bryanj

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Re: Pitted journal and bearing
« Reply #11 on: January 06, 2017, 12:17:17 PM »
1200 is too rough, i got some 3000 somewhere, otherwise known as bog paper with pimples!

 

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