400 four main bearings - will need replacement STD bearings.

[McCabe-Thiele (Ted)]

Ted, I strongly suggest that you buy a Clymer or Haynes manual for your bike and read the section on measuring and selection of bearing shells.
It will save you having to ask so many questions on here. These engines and tolerances are nothing like old car engines.
The colour codes are selected for a brand new engine assembly with no wear on the journals.
If there is any wear on the journals now then the codes probably don't apply any more. The journals need to be measured very accurately,  as has already been mentioned.

I have a Haynes Manual & a Cycleserve Servicing manual that came with the bike. I've found the Haynes one to be less than ideal as it covers the CB400 & CB 550 Uk & US versions & many of the sections seem unlike my bike. I will take a look at the section on journals as you suggest it might clarify what looks to me like a very over complicated situation. 

I ask questions as I am looking for the correct answers I do not understand so much about these engines. I appoligise if you find my thirst for knowledge in some way too basic, tiresome  or too numerate. I have a sound long standing knowledge of car engines spanning decades - I find a bearing shell marked as STD to  then be colour coded to more exactness an alien concept.

[taysidedragon]

Ted, I  didn't mean to criticise you, just pointing you in the direction of the knowledge that is necessary to get these engines right.
The manual section on bearing codes clearly explains the colours/sizes available. It helps me to have prior knowledge on things like that before I get into the guts of the motor.

[McCabe-Thiele (Ted)]

Ted, I  didn't mean to criticise you, just pointing you in the direction of the knowledge that is necessary to get these engines right.
The manual section on bearing codes clearly explains the colours/sizes available. It helps me to have prior knowledge on things like that before I get into the guts of the motor.

Hi Gareth, No offence taken I'm just being a bit contextually oversensative making me defensive.  I blame lock down making me a bit stir crazy, putting up barriers in my mind to the point where I wish I had never split the dam crankcase. I've felt completely out of my comfort zone for the last couple of days - that's not the normal me. I've read the section in the Haynes Manual as you suggested tbh it makes sense so I have a plan.  I'm going to measure up the main journals at 90 deg intervals and record the findings on a Excel chart. I have a couple of friends who are skilled in micrometer work that can help me out. That will enable me to make the right choice of main bearing replacements I need. The big end shells are all good thank goodness.
Cheers Ted

[Trigger]

As we used to say in the trade Ted, "you old boys worry too much ".
You just have to get your head around it. Forget everything you know from the past on English cars and bikes. It confuses my head the other way round as, i learnt Japanese engineering first so, when i look at a english built engine i wonder how the hell it ever worked    The Honda engine relies on high oil pressure to float the crank and cam on a very thin film of oil.
   
Japanese engineering was a cut above the rest when they started all those years ago. It is a bit like racing engineering with the clearances and balance of the engine to enable a high revving engine. Down load a Honda Manuel and as you have the basic's so, it should come clear.   

[AshimotoK0]

Eees a seemple  says Manuel 

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A old guy I know owned a Vincent Comet and Moggy 1000 Traveller from new in the mid 50's. He changed the oil in both machines religiously, probably sooner than required and he used both  as his regular transport until 2010. The Mog had done 300k and never had the engine rebuilt so he stripped it and took the crank to  Alex Carrs in Hull (Orcadian will know them  ) and they told him that the crank was still in tolerance.

I think it's all about oil changes and probably the luck of the draw with many old Brit engines.

Trigs right, download the manual from the Dropbox links and read several times and it all makes sense in the end. Getting Black & Blue  mains shells for the 400 is another matter as they are rocking horse poo.   

[McCabe-Thiele (Ted)]

I agree about oil & filter changes I had a Manta GT/E that eventually started to get a timing chain rattle at 120,000 miles due to tensioner travel  issues. I had to take the cylinder head off to remove the front timing cover - almost everything I checked on the head, the bores etc was within manufacturers tollerances - I had owned it for most of it's life being a stickler for oil changes every 5k miles or 12 months. Never used cheap oil unless it was fully synthetic. Likewise I sold my Mk2 Carlton 2.0CDi at 190k miles - it never had a camshaft or chain replaced - my brother had it off me befor parting with it at a tad over 250k miles. Body work eventually rotted out.