Topic: 400/4 Crankshaft bearings headache!

[MDW]

Hi

I am a new member to SOHC and hope someone can help on what must be a common problem. I damaged a main bearing/shell  disassembling the engine. There are no color codes on any of the bearings. On the back outside of the bottom engine casing I have these letters BBBAB. On the crankshaft itself I can only make out a couple of "A"s and a "1". I tried to use a bore dial gauge to measure the diameter of the casing without shells and the diameter of the crankshaft journals. I used palastigauge and the bearings are within the service limits. When I look at the chart from the service manual the closest match between crankshaft OD and crankcase bearing ID is D "yellow". However, I am not convinced that I measured the ID accurately as it was at the limits of my bore dial gauge. So, to my questions:

 - Is it critical to get exactly the right bearing?
 - Does anyone know what the thickness of the different color bearings are? I though the easiest approach would be to measure the thickness of the bearings I have and then match those to the closest fit to the new one
 - Is there another way to identify the correct replacement bearing

Any thoughts?
Thanks !

[Flyin900]

The case codes correspond to the correct size and colours of bearings, usually listed by colour in a FSM or possibly online. David Silver Spares has a US outlet and normally has OEM Honda bearing shells listed for sale. He has a special interest in the CB350F and CB400F, so he can be a good source for info and parts.
Regarding the clearance I am unsure there, yet Honda engines are usually very tight tolerances overall, so I would want to install the correct shell per the code on the case.

https://www.davidsilverspares.com/CB400F0-SUPER-SPORT-1975-USA/

[Tim2005]

It's best to get the correct shell, if it's not available then go for a tighter one.  In your circumstances I would get new yellows for that journal (if you can get them, some sizes are rare nowadays) then check them with plastigauge. That should give the  most confidant outcome.

[bryanj]

You dont need a bore gauge to measure the cases, that is what the letters are for, is it one of the B's you need or the A?
Get the pin in question measured accurately by somebody used to using micrometers in metric to 3rd decimal place then use the cross reference chart in manual or parts book

[MDW]

You dont need a bore gauge to measure the cases, that is what the letters are for, is it one of the B's you need or the A?
Get the pin in question measured accurately by somebody used to using micrometers in metric to 3rd decimal place then use the cross reference chart in manual or parts book

It would be a "B". I have a micrometer that goes 4 decimal points, but what is the "pin" you reference?
Thanks.

[MDW]

It's best to get the correct shell, if it's not available then go for a tighter one.  In your circumstances I would get new yellows for that journal (if you can get them, some sizes are rare nowadays) then check them with plastigauge. That should give the  most confidant outcome.

Yellow is the closest buy my estimations. Tighter means more oil flow, or the opposite? Thanks

[MDW]

The case codes correspond to the correct size and colours of bearings, usually listed by colour in a FSM or possibly online. David Silver Spares has a US outlet and normally has OEM Honda bearing shells listed for sale. He has a special interest in the CB350F and CB400F, so he can be a good source for info and parts.
Regarding the clearance I am unsure there, yet Honda engines are usually very tight tolerances overall, so I would want to install the correct shell per the code on the case.

https://www.davidsilverspares.com/CB400F0-SUPER-SPORT-1975-USA/

Thanks. Yes, I buy stuff from David silver and they appear to have all colors of shell bearing.

[bryanj]

Main bearing on crank is known as a "pin" as is the big end, 5 mains 4 ends

[Don R]

 A friend has been in the Honda business since the fours came out and still is, any question about bearings gets the same answer- green. 

[Tim2005]

Yellow is the closest buy my estimations. Tighter means more oil flow, or the opposite? Thanks

Sorry, I mean tighter clearance. So if yellow is too slack then green, then brown, then black, then blue.