Main bearing and primary guides advice

[Oddjob]

There is a chart in the workshop manual and the parts book which you use the markings you listed to work out the correct shell size. Not green shells, too small. In order of thickness it goes on the 400, blue, black, brown, green, yellow, red. You could fit blue and just run it in slowly, black is the correct size but brown is a size under the correct size but at a real pinch you could use those. I was told by a Honda trainer it was ok to go up or down a size but not down 2. Ideally not up 2 either but at least the excess will wear away with a good running in..

I would suggest a polish would make the gap bigger as well. Plus for the cost of that just buy another crank, try and find one with the markings visible and ideally with the letters B on the crank journals not C. I doubt your engineer friend knows how fine the tolerances are on Honda cranks or he'd have agreed the crank is past it's best. Price up another crank, it's probably for the best.

[davidcumbria]

Here is the link I used for my 550 shells from Japan
https://en.impex-jp.com/catalogs/moto/honda-other/cb550/cb550k-a-1976-usa-6724/camshaft-crankshaft-455707.html

[Fleabie]

Hi all,

Thanks for all the previous advice. It's all been very useful.

Well after much hunting I found some 'new' blue main shells. I could not get hold of the black ones for love nor money. So I have had to go up a size, which by all accounts is safe to do, as long as you run it in sensibly. I say 'new' because these shells are not in original Honda packaging but they have been carefully labelled with the correct part code in hand writing. I can also see the blue dot of colour on their sides, so that's very reassuring. So fingers crossed, they are what they have been sold as. I am going to clean up my case and check the shells with plastiguage.

The shell's look 'new', but they have horizontal marks across them i.e. perpendicular to the direction of rotation where you would expect to see marks on shells that have been used. Attached are 3 pictures of just one 'new' shell. Perhaps they have been tested in a crank case, and then found to be not suitable? But I would not expect a new shell to have any blemishes. The blemishes seem light enough to me but just want to check in with the experts :-) N.B. As before, these images greatly exaggerate how they look in real life ! Please bare that in mind when viewing the images. Is it normal for new shells to have these blemishes?

Thanks in advance!

[Nurse Julie]

Typical New old stock that haven't been stored in the original brown oiled paper.

[Bryanj]

Yup, bad storage

[Fleabie]

Ok, thanks for the replies.. Does this mean they are unusable?

[Bryanj]

No, useable just run in with care

[Fleabie]

So the saga continues... slowly. I fitted and torqued down the <cough> "new" blue main shells with plastigauge. The first plastigauge I used (PL-X) showed a clearance>0.045mm (i.e. off the scale for that plastiguage type).So I then bought plastigauge PL-A and this shows a clearance of more like 0.076mm which means the clearance is at the service limit (0.08mm). So what to do next :-(

Originally I a was trying to source black shells, but I cannot find these for love nor money. I am beginning to wonder if black ones would give quite high clearances. So what would people do next ? Go the other way and get a set of brown main shells ones ? (seeing as the clearance is so large with the blues.)

TIA, Bill.

[Bryanj]

Its inside the limit so use them

[Fleabie]

Thanks Bryan. Your help is much appreciated :-)

Would there be any harm in fitting brown shells? Would they be better in the long run as it would give a a tighter main shell clearance ? i.e. better oil pressure, longer life of engine etc?

[Bryanj]

I thought black was thickest then blue, if so brown would be even looser

[Fleabie]

I could be wrong here but I think it goes brown, black then blue in terms of giving increasing mains clearance. I got this from looking at the shell tables on page 32 of the manual on Ash's link:

(https://www.dropbox.com/s/1n3w5433jkph228/350F%20400F%20_4%20Shop%20Manual.pdf?dl=0)

I think that if have (according to plastigauge) approximately a 0.08mm clearance at the moment with blue shells, if I went down to browns I could knock of 0.02mm bringing it down the clearance to 0.06mm. If that's right then perhaps I could go even further down and go for green main shells as this would bring the clearance down by 0.03mm from the blues to 0.05mm. Although a 0.05mm clearance is above ideal, its much well within the upper service limit of 0.08mm.

Would anyone agree/disagree? If I am going to do this, it might as well be as best as I can get it :-)

[Bryanj]

I think you are reading it wrong, smallest journal with biggest case hole needs thickest shell(blue)

[Fleabie]

Sorry, I am being a bit dim   Your are right, I was reading it wrong. The way you worded it makes perfect sense now. So yes, I guess it’s stick with the blues or get a new crank (as you advised earlier in this thread).

Thanks Bryan!