Topic: Codes stamped into crankcase halves?

[750K4]

Has anyone come across a way to determine what the codes stamped into the crankcase haves represent?
My '69 750 has a 4-digit number/letter combination stamped into the rear faces of both the upper and lower crankcases.
I assume it's a date coding of some sort. I searched the archives and came up with nothing. But I'm pretty sure someone has asked this before. What gives?

[puppytrax]

My '69 750 has a 4-digit number/letter combination stamped into the rear faces of both the upper and lower crankcases.

Just a WAG...maybe to keep the align-bored halves from getting mixed up??  As it goes down the assembly line??   

[jtb]

Used with a chart in the honda manual, it will tell you which mains and conrod bearings to use.

[puppytrax]

Used with a chart in the honda manual, it will tell you which mains and conrod bearings to use.

That would be useful to know...I could check eBay for some NOS mains/conrod brngs without opening the case...

Where abouts in the manual??? I'm looking; don't see anything yet...   

[aptech77]

Yes, it is to indicate main bearings in relation to crank size.

[bryanj]

Should be just letters A,B,C,D and its the sizes of the main bearing holes in the cases, The pin size codes are etched onto the crank and rod size codes on the rods so you cant order shaells untill its in bits sorry.

[750K4]

I'm not sure we're talking about the same codes. These are hand stamped codes, not the cast-in ones on the top rear of the case. These are on the rear face, above and below the parting lines of the two case halves.

[puppytrax]

I'm not sure we're talking about the same codes. These are hand stamped codes, not the cast-in ones on the top rear of the case. These are on the rear face, above and below the parting lines of the two case halves.

I have a 74 and 76 CB550 motor sitting out of the frame, and neither have hand-stamped numbers, and no stamps whatsoever on the rear parting line.

Maybe only a 750 thing, or added at some time after purchase (rebuild?)...   

[Bodi]

I've seen motors with and without the codes, why I don't know. The codes signify the main bearing bore diameters in the case. I've heard different stories as to whether "we" can use them or if it's just for the factory: either you can use the code and the code or colour blobs on the crank to pick bearing shells (there's a chart in the service manuals that suggests that's true) or the code letters are just a factory reference and you should measure the bores with a bore micrometer or use plastigage and a set of (any size) bearing shells to get the clearance and then use the correct shells. I do the latter, anyway. Since I don't have the micrometer I have never tried to compare the codes and actual sizes.
And how the heck could you bore them different sizes anyway???
And then the theory that you just use the thickest shells and break her in carefully... that one sounds fishy to me.

[bryanj]

Bodi, i can tell you using the thickest shells works, i done it many times! the holes can vary in size fractionally due to "whip" in the boring bar whilst cutting and the micrometers just aint accurate enough--in production air gauges are used.

[nippon]

Hello,
I've got a stamped code in the rear of the upper crankcase, too.
I' don't think that it is a date, I've got a 71' K1 engine with a matching engine number,
so I' don't know the meanig of of the code. sorry. But, I would like to know it, too.

Yes, the stamped code in front of the upper case is for the crankshaft bearings.

nippon