New Main and Big End Bearing Shells

[adriangsmith]

what is the consensus regarding ordering new bearing shells?
Do we go by the original markings or do we need to measure the diameters to allow for any wear?
I understand the procedure for matching the originals via the stamped markings but concerned about wear on the journals etc.
Also i cannot read the size markings on my conrods. I can see the letter K on all of them but no further markings.

At £180 all in i don't want to get it wrong!

[AshimotoK0]

Really one for Oddjob, Bryan or Trigger .. I would run your fingernail across the journals and see if there is any scoring or or obvious visible wear. The crank stampings, relating to the journal sizes,  are only valid when the crank was new. Also send us some close up shots so that we give you an opinion. I had mine 'mic'ed up' by someone who had the right micrometer, experience and feel. At the factory they would have used air gauging to measure them.
 
Take digital photos of where the con rod marks should be and play around with the contrast on the image and they will probably show up. One letter is for the weight and the other mark  for the big end shell size OD (obviously this dia.  doesn't wear unless the shell has rotated in the con rod which is highly unlikely IMHO).

The attached service bulletins are useful.

[Trigger]

Need to see the letters, numbers, crank, con rods and old shells.

[adriangsmith]

Hi All,
Here is what i have so far:
crankcase BBBBB
Crankshaft AAAAA 4444

All crank journals measure at 35.96 - 35.97 (will take it into work tomorrow and measure to 3DP)
Main scoring is on the centre main journal.
All main shells show a pitted finish but not through to the copper.
All big end shells are through to the copper in places and some are scored, no scoring seen on the corresponding crank journals.
Pictures below.

[adriangsmith]

Hopefully this shows the state of the big end shells

[adriangsmith]

Hi OddJob,
K is the heaviest weight and this is an F2 engine.
according to the chart i have the mains should be a letter/letter combination as shown here:
http://www.hondachopper.com/engine/diagrams/images/crank.parts2.gif
where the conrods shoud be a number/number combination as shown here:
http://www.hondachopper.com/engine/diagrams/images/crank.parts1.gif
Please correct me if im reading this wrong.

So mains would have been all greens
And big ends would have been all greens also

Based on the wear measured on the journals should i replace them all with blacks?

[Trigger]

From the pictures the crank looks finished on the first picture but, hard to tell unless up close and personal.

[Trigger]

As Trig says it is hard to make a determination on the state of the crank from pics. However try this and see what you think.

The centre mark in the main journals is where the oil groove runs, you'll see on the shell that it has a recess there to allow oil to spread across the shell, as this part doesn't touch the crank journal it doesn't wear it so if that centre section is higher than the rest that shows the crank is quite worn. Just because they are shiny doesn't mean they are worn, run a fingernail across the journal and if there is a ridge where it meets the oil groove then you'll have to think about a replacement crank.

Zoom in Ken and tell me if my eye sight is going but, I see more pits than a teenager getting over acne

[adriangsmith]

Thanks all,
No pits on the crank shaft just the faint score lines.
I'll give it a wipe over and take some more shots.
Big thanks for the service bullitins Ash, very informative.
Adrian

[adriangsmith]

cleaned and checked. no obvious ridges on the mains but they feel a little rougher than i would expect.
Also included an image of the old main shells, all of them worn pretty much the same as these.

[adriangsmith]

The cam journals are what caused me to strip the engine again.
It suffered a top end oil feed failure due to a grain of sand stuck in one of the metering jets!
Found a new cam tower, just need to find a camshaft now as the right hand end is chewed up beyond repair.
Oil pump is on my list for a strip and rebuild.
Must admit the engine seems to have had a hard life and lack of maintenance.
When i bought the bike it had not been on the road since 1986.
I did a top end rebuild to replace the cam chain and tensioners, tensioner wheel was completely worn away, blade guide slots in cases worn as well.
So here i am again doing the job properly with a full rebuild.
Black shells readily available from DSS and strangely enough are cheaper than the others. but will probably follow your suggestion and go for a set of browns.
Thank you all for your help and advise.

[royhall]

Whilst there's no facility for regrinds you can have the journals micro polished. Not sure who does it, but Rick Partington of Classic Bike had the 400 he was building done. May not need it though.

[hairygit]

Before completely giving up on the can, give S.E.P. in Kegworth a call. I gave seen them repair cranks that look like ploughed fields by submerged argon arc welding the journals, then grinding back to original spec, and the crank is then good for many years to come. Chances are the journals on your cam may respond to the same treatment, and may prove easier and cheaper than trying to source a replacement.

Sent from my X6pro using Tapatalk

[AshimotoK0]

Whilst there's no facility for regrinds you can have the journals micro polished. Not sure who does it, but Rick Partington of Classic Bike had the 400 he was building done. May not need it though.

I do have a spare  (bare)  crank that I got miked up by my 'miking' expert and the journals were all  good. Sadly he passed away last summer, very suddenly. Think it 'owes me the 'ubiquitous' 25 quid (it was off a K7 but all cranks basically the same, up to the auto), but your crank is probably recoverable anyway by the sounds of it .  Yes that article by Rick Partington in CB was interesting .. the kind of article they should be doing rather than one I read on bead blasting ..where, at the end,  they basically told you in CMM to give it to the experts (and pay an enormous amount of money). That mag went sadly downhill when Rod Gibson passed away

BOT are you guidance on this, IMHO (Bryan, Oddjob Trigger  )

[ginger_jim]

Before completely giving up on the can, give S.E.P. in Kegworth a call. I gave seen them repair cranks that look like ploughed fields by submerged argon arc welding the journals, then grinding back to original spec, and the crank is then good for many years to come. Chances are the journals on your cam may respond to the same treatment, and may prove easier and cheaper than trying to source a replacement.

Sent from my X6pro using Tapatalk

+1 sending to SEP, they will provide the shells too.