SOHC.co.uk Forums > CB500/550
Crank not rotating
murdock:
bingo ! I scared you!
change that , the 2 , apart from that strange crater has marks ,think in microns !!!! check them very well with a magnifying glass, the best thing would be a plastigauge test .
McCabe-Thiele (Ted):
It's surprising how easy a binding can happen, on my assembly a con rod had a high spot from burnt oil residue on the back holding the shell proud.
Pleased you appear to have found the reason.
alexdecker:
--- Quote from: Oddjob on May 07, 2022, 02:50:02 PM ---Looks to me to be a rust spot. When the bearing was removed it allowed the rusted area to expand (which it couldn't do before due to the crank stopping it) this then bloomed out to look like it is now.
Check all the others for similar damage, you're probably lucky as it's extremely rare for this to happen in my experience. You could just replace this bearing with another green but I'd strongly advise buying a pair of green bearings to replace those on that journal. Don't order new ones until you've checked the others very carefully.
Your lucky, green is about the only colours it's still easy to find. Yellows and blacks are rare and browns are starting to go the same way.
If your stuck finding new bearings contact me as I have quite a few NOS ones. I started to collect them many years ago and it's coming to the point where I'll sell them all and cash in. As soon as I've finished building the engine on my last restoration I'll be selling a lot of stuff.
--- End quote ---
Thanks all for the encouragement! This had me feeling rather hopeless for a minute there. I will be so much more equipped for a second restoration, now knowing how many things to be aware of all the time.
I like the explanation with the rust spot having expanded - mostly because I expected them carefully taking them off, and am sure it wasn't there. But didn't expect them going in, other than making sure they came into the same place where they left.
I inspected them all again now. I have a few questions.
1. I have one black one with a tiny speck of a dot, that may actually have been how the other bearing looked like before that rust spot expanded. Nonetheless - is this usable? I have checked the journals on the cam, and they are all silky smooth with literally nothing in terms of spots, scratches etc. See photo below.
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2. I have to other bearings, both brown, with wear like this (the top part of the bearing. Easier to see when zooming in). It feels smooth when I run fingers or nails over it, but it still looks… weird. Don't know if this is usable? Again, the journals have no damage whatsoever. See picture below.
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What do you guys think?
Incidentally, I found a guy over here, who sells a brand new crankshaft and a brand new cylinder block for what amounts to 230£, which I thought was fairly cheap. Still glad I don't need it though (hopefully).
I ordered some plastigauge, and am going through all of them next week.
Oddjob:
The black one I'd replace, both of them, it's not really a good idea to mix a new and a worn one on the same journal. Left in I think it will end up scoring the journal surface. The black shell can only have come from either number 2 or number 4 journal, as the ONLY combination to use a black shell is a C2.
As I said though, finding black shells is difficult, 13315-323-000 is the part number, CMS did have some months ago but they've gone now and they weren't cheap when they were available, they are showing them as selling for £11.25 or so but I can guarantee that when they were available they were a LOT dearer, I think they reduce the price of the part when it sells out so that they can buy someone else's stock and claim they aren't worth as much. Sure they were close to £28 a shell when they did have them, plus P&P of course.
I'm not keen on the state of the rest of the shells TBH, that scoring on the upper edge is worrying, not sure how long this engine may have been stood but to me the surfaces of the shells look contaminated and that's why they are starting to break up. I'd replace all the crankshaft ones if it were mine, I'd also check the rods shells just in case.
£230 for both or each?
Bryanj:
That looks like physical damage and/or badly contaminated oil to me, BUT i would far sooner have them in front of me and not in a pic.
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