Spec'ing mains and big end bearings

[neevo]

I'm going to replace all the mains and big end bearings in my CB400F motor as there is some slight scuffing on some and to be honest, I've replaced nearly every other part... so why stop now.

Call it cheap'ish insurance.

I understand how to use a plastigauge however I have some questions about when to use it.

Do you have to buy new bearings first? I assume that gauging the old bearings is redundant as they could have worn.

Any help is appreciated, also it looks like new bearings are not generally available, so will that play a role in which ones go back into the motor?

David Silver Spares seems to have black/brown/green/yellow in big ends but only black/brown in mains.

 

[neevo]

Also checking my Haynes manual it references the big end and camshaft journal clearance (I assume this is the bearing shell clearance) as 0.018 - 0.048mm

The bearing shell chart confuses the shit out of me though. God knows how you read that:

 

[neevo]

Not much input, oh well. Here's what I was going to do.

1. Install the cam and big end bearings
2. Plastigauge them and check tolerances
3. Measure existing bearings and replace based on plastigauge measurements (eg if plastigauge is in spec, simply replace bearings for the same)

Hopefully someone has some inputs.

 

[notlob]

You should replace with the same colour code as the existing ones unless you are having the crank reground. For the mains the codes for each shell are stamped on the crankcase match the upper and lower numbers to the ones in the table to get the correct colour code and for the rods on they are on the crank web. You shouldn't need to install the cam to get the readings.

Plastigagng the old shells first will tell you if they need replacing, but wont tell you if there is wear on the crank, you will have to use a micrometer for that. If your satisfied that the crank is OK then go ahead and buy the right colour coded shells. Install then and then plastigage again to ensure they are OK withing tolerances, not unheard of for them to be too tight.