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Author Topic: U870 on engine cases  (Read 1191 times)

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Offline tx750

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U870 on engine cases
« on: June 16, 2007, 03:38:08 PM »
Hi all,
I have a question about these numbers and letters on my 1974 CB750K.I was changing the oil the other day and noticed that there was a big "U870" stamped on the engine cases top and bottom just to the right of the oil filter housing. Looks like it was done with a rubber stamp and ink.Also stamped into the metal there is the letters "ABBAB".Can anyone tell me what these mean for sure? ???Thanks!
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Offline Bodi

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Re: U870 on engine cases
« Reply #1 on: June 16, 2007, 07:31:37 PM »
U870 I have no idea, the ABBAB is a production measurement code for the main bearing bores. There's a chart in the shop manual to pick bearing shells according to the case and crank codes, but I prefer to plastigauge them.
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Offline tx750

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Re: U870 on engine cases
« Reply #2 on: June 17, 2007, 09:53:51 AM »
Hey thanks, Wasn't sure i have another cb750 engine that has the ABBAB but not the U870 that one has be scratching my head
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