Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: eem46 on November 09, 2021, 01:21:22 PM
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Dear All, I want to build up a new cb400f engine but checking the crankcases after washing them, I see and feel with my nail that the gearbox rollerbearing made markings in the crankcase. Is this bad? Did the bearings spin around, because of not enough pre tension? Can I use the crankcase? Shall I glue the bearings in with Loctite? Please advise. Kind regards Emiel
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Yes, it shows the bearing was spinning at some stage.
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As Julie says they certainly look like rotation marks a lot might depend on how bad they are as to whether you can use the casing again using something like Hondabond on assembly.
Personally I would be looking for some replacement casings - others here might have experience of this issue and be able to tell you the outcome that worked for them.
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Very rare occurance, what does the outside of the bearing look like and does it rotate smoothly?
2nd Q is is this going to be a low mileage occasional ride or a thrash it everywhere daily driver?
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Hi, I bought the empty crankcases with some spare parts. So sadly I have not the ‘matching’ bearings. It will be a low mileage bike, but all new engine parts. So if it is not worth it, or a big risk I will trash them. Loctite has nice versions to glue bearings, and fill gaps. Worst case I need a new set, which is a shame.
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If it is not going to be a high mileage thrasher, i would bolt up the crankcases with the shaft and bearings you are going to use and see if there is any play.
Loctite will take up quite a clearance safely and is a good solution as long as there is no actual play in the bearing to case
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Looking at the second photo I do not recognise the shot of the alloy bar across the casing base is it a early 400 engine or have I already forgotten what they look like inside?
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Looking at the second photo I do not recognise the shot of the alloy bar across the casing base is it a early 400 engine or have I already forgotten what they look like inside?
The view in pic 2 is showing this area as highlighted in my photo Ted
[attachimg=1]
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Worth cleaning the joint faces of the cases then assembling with both those and the bearings completely dry, then you can at least judge what you've got there and if it's practical to use it.
Does it clamp the bearings, or do they just fall out ?
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Nurse Julie I clearly have the memory of a Goldfish - the Castle is a surprise every time! lol Ted
Credit to Ani DiFranco lyrics.
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Thnx All, will dry build this weekend to see if they clamp.
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Take particular care to remove the sealant that appears to be around the bolt holes in some of the pictures as that will change the dimensions if left there when you assemble it.
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Castle? what castle
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Just thinking outside the box for a moment are the same corresponding marks on the upper casing as well?
Not sure from your comments if you definitely have a matched pair of casings when you bought them.
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There are only 1 set of markings for mains size
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There are only 1 set of markings for mains size
So the outside diameter of all main bearings are the same the bearing colour codes just refer to the thickness / inside size /clearance of the shells.
If the crankcase is not paired with the original crank then you have to ignore the crank case codes and work off measurements only. (Edited to include case)
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No Ted, each crank is sized and marked, every rod is sized and marked for both hole diameter and weight the cases are measured on each hole for size anf cases marked.
I have yet to find anybody, including myself, who can measure the pins or holes with micrometers to the accuracy Honda called for.
Honda used air gauges which feed a known air pressure into a perfect sized plug or ring with holes and the amount of pressure drop is related to size of pin or hole. This method is accurat to 3rd decimal place in metric.
The shells are sized for thickness simlarly and selected to give the correct oil clearance, remember Hondas were builtwith clearances such that running in was not required, just a "bedding in" of running surfaces as Kawasaki found with the Z1000 having to rebore under warantee as people treated them too easy and bores glazed
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"If the crankcase is not paired with the original crank then you have to ignore the crank codes and work off measurements only."
As Bryan noted, that's not the case.
Concept is that all the bores and pins are measured at finish of production and remain valid (unless obviously worn) from then on. Those codes stay with those components for ever in the letter or numerical form Honda give them.
The compensating factor is the shells changing thickness to accommodate the different dimensions originally given. Cross reference the two components in their table and it'll give you a shell code to make up the difference in tolerances.
Scenario of using crankcase and replacing crankshaft would only change shell's designated if the original (non shell) codes changed.
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I am obviously getting lost here so to clarify - I thought the crank case codes were to help identify one measurement in the shell tables for the size of the mains - got that - the other axis in the tables is for the crank journal size.
If a crank case is coded say CBBC then this code is based on the main bearing holes in the crankcase being slightlt different?
If that's a yes then crankcase halves should match YES or NO?
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Going back to the original post I asked if there were any rotation marks on the upper half of the crankcase as this would help support that they were a matching pair.
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Dear All, that is the tricky parts of buying a empty set of crankcase, I dont know and I cant prove they are/were a matching set. Looking at other crankcases the marks are always in the lower crankcase. By the forces?
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Can you ever found out if a set of crankcases are matching? No secret Honda stamp?
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Nope, but over many years you usually find if they aint a pair at least one of the many machined holes you will find you can feel a step at the join
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Can you ever found out if a set of crankcases are matching? No secret Honda stamp?
You raise an interesting point - Honda did a nice big clear lettering stamp on the lower crank case with no alpha/numerical marks to say this crank case top matches the crank case bottom.
In my head I find it difficult to see how a rotating bearing would not mark both halves of the crank case in a similar though not necessarily identical manner - then again you mention the forces at work - rotational from the gearbox but with the down forces at the same time from the pistons on the crank maybe that explains why the marks are mainly on the bottom half - that makes sense.
If you have seen other cases where the marks seem to be always on the bottom half then that supports your explaination.
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Rod shells are always more worn on rod side not cap, it takes 3 of the 4 strokes load, never really noticed any difference on mains and as ball/roller casings are not supposed to totate in housing i have no idea
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My 50cc Kreidler moped has special code to see of both halfs are matching. Strange that Honda leaves that ‘option’ open. Even on the picture of Julie you can see that the rollerbearing makes a mark. But ofcourse a mark or moving slighty material is different.