Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Deano400 on March 10, 2022, 07:57:24 PM
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Just taken the conrods off the crank to check the condition of the shells and was surprised to see three of the pairs of shells had Black markings. The reason I was surprised is the conrods are marked with a 1. I was expecting conrods marked 1 to have either Red, Yellow or Green shells.
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I used plastigage to check the clearance which looks ok.
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The forth conrod was clearly Green shells with a 3 on the conrod so appears fine.
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Everything seems fine just confused with the Black markings on the shells. No visible markings on the crank to help me.
So I suppose my question is, could they be red shells that have gone black with age and heat? Bearing in mind the Green shells are clearly Green.
Any thoughts and experience would be appreciated.
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It's quite common practice to use black shells instead of the correct colour. Reasons can be, the correct colour wasn't available, reds are hard to find for instance. Or the owner couldn't work out the correct colour for himself for some reason. The trick of reading the letter and number codes wasn't commonly known until a few years ago unless you were in the trade.
If you use black shells, which are the thickest shell, all you need to do is run them in very carefully and they'll wear to the correct thickness over time.
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The table is for new parts. It is only good if you are using a new crank and rods and not for second hand parts which is worn ;)
Looks to me like it has been measured up by an engineer and shells fitted for the correct clearances.
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Thanks Ken and Graham.
The more I look I'm pretty sure they are Black and not discoloured. The fact that the plastigage looks good I think what you are saying Graham is probably the case. Thanks again.
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Thanks Ken and Graham.
The more I look I'm pretty sure they are Black and not discoloured. The fact that the plastigage looks good I think what you are saying Graham is probably the case. Thanks again.
Without seeing it up close and personal, i would say it has been re-shelled before.
I have had so many members engines here over the years that they have rebuilt by the owner with advice on shell codes from other members on the forum that always point to the chart in the workshop manual and it has made a mess of there crank. If the plastigage is good, then that is the correct measurement ;)
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Definitely been apart before Graham, enough Hylomar Blue inside for ten engines.
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Thanks Ken and Graham.
The more I look I'm pretty sure they are Black and not discoloured. The fact that the plastigage looks good I think what you are saying Graham is probably the case. Thanks again.
Without seeing it up close and personal, i would say it has been re-shelled before.
I have had so many members engines here over the years that they have rebuilt by the owner with advice on shell codes from other members on the forum that always point to the chart in the workshop manual and it has made a mess of there crank. If the plastigage is good, then that is the correct measurement ;)
Name one.
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That would be unprofessional in my business as, I have a very good customer relationship .
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There's a very old saying that goes
"Put up, or shut up"
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I’ve now checked all the conrods with plastgage. The three Blacks were all good. The conrod marked 3 with the Green shells appears to be right on the limit.
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Am I right in thinking that going to Brown shells would be the right move? TIA.
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TBH Deano the fact the blacks are correct sort of proves the point about fitting blacks in the first place. They have clearly worn to the correct thickness which is essentially what they were meant to do by fitting them in the first place. The green however being the second thinnest shell hasn't been able to do that. You could either try another set of blacks (if you can find any) or fit browns as the next size up.
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Thanks Ken,
DS have both Brown and Black in stock at the moment. At £25 a pair I think I'll try one of my current Black sets and see what it looks like using Plastigage. I know it's not ideal as they have some wear already but if they are tight it would probably point me towards Brown, if good clearance then go with Black. If that all makes sense? Any thoughts welcome.
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If you fit Black expect a tight fit with minimum clearance or even less than that. The idea is to do a really careful run in period so the shell wears to the crank, I'd also find it interesting if you fitted a new black shell where the old blacks are and see how they compare in clearance, I'd expect it to change to much less clearance which would prove that's why the PO fitted them. Maybe at the time he couldn't find 4 sets of black shells.
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I've fitted a pair of the 'bedded in' Black shells in place of the Green.
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Not tight so I think I'll go with your recommendation Ken and go for Black shells.
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What clearance would new black shells give I wonder, be interesting to find out and would show how much the old blacks wore to suit the crank.
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The new Black shells are pretty much the same as the 'bedded in' ones. So very little in the way of wear on the old ones. Having said that I haven't a clue how many miles were done by the PO on the shells.
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The colour on the shells fade quickly so, the ones in your picture look nearly new and that would explain the different shells to the codes ;)
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Makes sense to me Graham. I guess when the PO fitted the shells he couldn't get four sets of Black so fitted one set of Green. Anyway all Black now and clearance looks good.
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Green to black is ok but, yellow to black are too tight ;)