Topic: different advices on choice method for the journal bearings of 750 and 500

[_mark]

Hi everyone.
I was just reading the shop manual of Honda CB 500 and I found that, differently from the 750, they declare to do NOT trust the stamped letters and numbers for the choice of the crankshaft and connecting rod bearings.
They tell to use the dial bore gauge and plastigage and then, based on the clearance value, to buy the bearing's shells. The numbers and letters are only "product's coding" that have nothing to do with the maintenance.

Why Honda decided in the shop manual of such bikes (750 and 500) that were engineered at same time to "mislead" the customers in two different methods ?

thanks and Regards.

[bryanj]

I don't know of anybody, apart from a full time engineer who can use dial gauge and micrometers to be as accurate as Hondas original air gauges used in production.
unless you spin a set of shells the casing will not wear, and if you have its scrap anyway.
the crank may wear very slightly and so the best method is to work out from the codes what shells you should fit and check with plastigauge

[rotortiller]

Follow the book. Plastigauge is to verify clearance after using the Honda method of bearing selection, then if you have an issue you know where to go selection wise. You should in all cases as a first step associate crank and rod journal size with micrometers to verify the coding and check the case and rod bores with bore gauge after case clamp up then select bearings with final plastigauge verify. You will be fine so long as the clearances check out, or coding matches your measurements prior to bearing selection.

[_mark]

thanks, these answers are all true but my question was more addressed to understand the reason of such discrepancy in 500 and 750 workshop manual.

[bryanj]

The pic you show seems to be saying use the codes on cases and crank but as i dont speak the language i can not be certain.
Which manual tells you to measure ? I dont remember reading that in any dealers manual i used

[_mark]

The pic you show seems to be saying use the codes on cases and crank but as i dont speak the language i can not be certain.
Which manual tells you to measure ? I dont remember reading that in any dealers manual i used

this is the italian version of the manual, you can find the english one here

http://manuals.sohc4.net/cb500/service_manual/HSM500550_2.pdf

at page 31 of pdf "These (marked letter and numbers at factory) are production codes and should not be used or refered to during service or repair"

[Don R]

  It's a quandary, a dilemma, and a state of perplexity. And I just don't know. I have not always been able to reliably read the crank side of the codes or find color on used bearings. Plasti gauge may sometimes be the best available method.
  A well-known Kawasaki mechanic and racer mentioned the tiny difference between the tightest bearings and the loosest bearings. He and Russ Collins were racing with heavy weight oil and just used the loosest ones.