SOHC.co.uk Forums > CB350/400
400 four main bearings - will need replacement STD bearings.
Bryanj:
In production Honda used air gauges to measure pins and housing which were accurate to parts of 0.001mm and as such could selectively fit parts to get the EXACT design clearance.
When did you ever hear of an "old" car doing 120 000 miles and on stripdown find everything in tolerance and yes i have seen that, chains were shot but all the rest was good enough to refit
McCabe-Thiele (Ted):
--- Quote from: Oddjob on March 21, 2021, 06:12:57 PM ---What journal was the green shell on Ted?
Must be either 2 or 4.
--- End quote ---
You are right Oddjob the Green Shell was on number 2!
As D6I-A was the bearings on 2 & 4 I guess they are both the same.
I have just removed the Conrods a C is marked on the front edge two of them have number 2 & 3 on the other side but they were not in the respective cylinder bore so I am thinking this number in black print is meaningless. They were all fitted the same way round as regards the side casing number on the side "S59" on all four.
Tommorow I will lift out the crank & check for markings on the shells being carefull they do not lift out with the crank. I will then check each bearing for any colour markings and double check the shell codes.
McCabe-Thiele (Ted):
--- Quote from: K2-K6 on March 21, 2021, 06:03:30 PM ---"I'm learning here I have never encountered a car with such complications as different coded journals on the same crank - wonder why STD didn't mean just that with oversize being +0.1 or whatever."
It is, in essence, a view of the lengths they went to in production tolerancing. Ordinarily in most process as it advances the tolerances are accumilative (unless by happy accident one error cancels another) with the accepted machine accuracy and repeatability available producing the components being recognized, the range of 5 different shell dimensions is planned to compensate for that process capability. It effectively pulls all of that production line tolerance back to as close to zero that they could get it.
In terms of "old money" a BMC A series built with en40b crank fully balanced, ground, nitrided, micro polished to perfection, with rods balanced end to end and rod to rod, etc etc, effectively the best hand finished blue printing only gets close to what these engines came off the production line as absolute standard. With near 100bhp/litre and usually ten thousand rpm ceiling to go with it, that really shows just how good this design and production was, that's in mid to late sixties and early seventies, there's nothing that came close to them.
--- End quote ---
Ah the good old EN40B nitride crank standard in all the S variants 970S, 1071S & 1275S that all takes me back to my teenage days K2-K6 !!
McCabe-Thiele (Ted):
--- Quote from: Oddjob on March 21, 2021, 09:17:00 PM ---Lol, Ted the numbers on the rods don’t refer to the cylinders they are fitted to, it’s how Honda identified the journal size so further down the production line whoever was assembling the engine just needed to check those markings and the letters on the crankshaft to know what colour to fit.
It sounds complicated but once you get your head around it it’s really very easy and logical
--- End quote ---
At the moment my head is awash with contradiction including the fact that when I split the crankcase it was almost perfect - no bits flying out everything stayed in the top half that was face down except the main bearing to number 5 journal that stuck to the crankshaft - the other 4 stayed in the casing.
Now here is an observation having just had a double Glayva to heplp me sleep tonight - the four main bearings that remained in the lower half of the crank case as I lifted it off all stayed in place. The one bearing that was stuck to the crankshaft does not sit as it should in the casing when I pressed it back in it seems looseish as it does not click into place like the other four. This bearing is the one that appears to be the worst for wear is there a reason for this is it connected to the proximity or not of the oil feeds?
I feel pretty confident that the casing has not been split before based on the 6 bolts being so tight, the white residue of what I assume is Hondabond & the brown staining of the engine casing. The drive chain is clearly worn consistent with being original plus the two guides appear to be made of solid black steeel like substance - it looks 42 years old.
taysidedragon:
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.
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