Topic: Looking for "A" crank bearings for 1974 CB550

[Hannibal Smith]

My crank goes A-B-A-A-A, I can get "B" from BikeBandit (great reliable company!) but they don't have "A"s.

My crank is a 24,000 miler with perfect journals, I could just button the bottom end back up with the old bearings, but since they are relatively inexpensive, I considered just putting fresh ones in-

Anybody have a source?

[bryanj]

Thats the crank codes but what about the casing codes and the cross refer to shell sizes?

[Hannibal Smith]

Now I am a little confused-

I will mike the journals tonight, but I checked the bearings (mains) and they are all marked D3K-A

My case is marked ABAAA, for my main OD's as bored in the case, but the bearings themselves are all designated as "A"s (just checked)

[Hannibal Smith]

Ok- Starting to figure this one out, via the bearing flowchart, the ABAAA on the case doesn't mean jack?

All things being equal here (I have 1"-2" external mics, but not an ID measuring tool)if the journal hits the window on the flowchart, then I still need to source "A" bearings if wear falls within my window when I measure tonight?

All current bearings are marked "A" and look good-

Since this is a factory assembly job, I will assume that my case boring falls within 1.4179" and 1.4182" as the "A" bearing only falls within this flowchart line and is not shared by any other case ID as is "B" for example-

[mystic_1]

The crankcase codes are only half of the puzzle.

There's a similar code on the crankshaft, usually on the side of the couterweight closest to the primary drive sprockets.

You then cross-reference each letter of the crankcase code against the corresponding letter of the crankshaft code, on the bearing selection chart.  This tells you what size shells were fitted when new.

If there's any wear on the crankshaft, you may need tighter bearing shells, but you won't know until you install the bearings and shells into the case, with some plastiguage to measure the clearance.

mystic_1