Author Topic: Crank not rotating  (Read 1958 times)

Offline Oddjob

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Re: Crank not rotating
« Reply #15 on: May 06, 2022, 10:47:53 PM »
Remove the gearbox, remove the camchain and primary chain and shaft. So just the crank is left in place. If it still won't rotate then maybe somehow you have bent the crank but I doubt it. As you tighten the bolts do each one a little, check the crank rotates after touching each bolt, keep doing that as you keep tightening the bolts, a little at a time. If the crank stops after tightening one specific bolt check the journals nearest to that bolt.

I'd also spin the crank with no bottom case on, see if you can spot anything wrong, like a bent end of the crankshaft.
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Offline McCabe-Thiele (Ted)

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Re: Crank not rotating
« Reply #16 on: May 07, 2022, 07:02:01 AM »
I think it very unlikely that you could have bent the Crank.
At the start of your strip down did it rotate freely?
If it did what is the range of the Crank case markings codes could you have confused number 1 cylinder with 4 it's easily done when stuff is upside down?
Plastigauge is where I would start now to identify the cause, Kens advice sounds a good starting point.
« Last Edit: May 07, 2022, 07:26:56 AM by McCabe-Thiele (Ted) »
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Offline smoothoperator

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Re: Crank not rotating
« Reply #17 on: May 07, 2022, 08:41:42 AM »
+1 on plastigauge measuring. Will let you know what your clearances are. Take your time, walk away from it for a while. When the plastigauge turns up, give it another go.
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Online alexdecker

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Re: Crank not rotating
« Reply #18 on: May 07, 2022, 10:55:31 AM »
Ok, did some extensive research this morning. I made several discoveries.

It turns out the crank seizes when I tighten down on a specific journal. My motor has the writing BCBCB on it. I am not sure about the color of the bearings though. But it seems to be one bearing in particular that makes the whole thing seize up.

Another thing I discovered is that the crank does not seem to rotate completely evenly throughout its motion. This is not visible to the naked eye, but when tightening down certain journals, I can feel the rotation taking more force throughout half the rotation. Not by a lot, but definitely noticeable. This could support a bent crank, but could maybe also just be the uneven tightening of the screws in this experiment?

Weird thing is that everything rotates freely and with no trouble before I took it apart. So something definitely happened along the way…

I am using allen head bolts with a washer, instead of the original bolts. Could that change anything in regards to the torque spec? When I torque the bolts down with my screwdriver, everything still rotates. But when torquing to spec, it seizes up on the on particular journal.

- Alex
« Last Edit: May 07, 2022, 11:27:02 AM by alexdecker »

Online Bryanj

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Re: Crank not rotating
« Reply #19 on: May 07, 2022, 11:54:10 AM »
From what you are saying it would suggest a bent crank, many decades ago i worked on an accident damaged 500 where the tapered end had been bent in the accident, we actually managed to straighten it with a specialy made bar and it did many years service BUT the crank rotated free all the time, it was not out of the cases ever.
I am negotiating with an ebay seller who tells me he has 2 nos cranks, i would like one to go with the nos cases i have, i could ask for a price for both if you wish.

Online alexdecker

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Re: Crank not rotating
« Reply #20 on: May 07, 2022, 01:32:04 PM »
Damn it.

Ok, assuming the crankshaft is bent and I need a new one. In that case, I don't need to measure anything, I can just pair the case markings with the crankshaft markings, and then get new bearings based off the result?

But what about the rod bearings? I assume I can't reuse the old ones, and would have to get new ones as well for the rods?

Offline Oddjob

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Re: Crank not rotating
« Reply #21 on: May 07, 2022, 01:42:01 PM »
So long as the rods aren't bent as well you can transfer them over. However, like you say the shells will need to match, you have a chance of that happening but I wouldn't count on it.

Have you checked the crank bearings, sometimes you can still see the colour on the side edge of them. Worth having a look.

I'd remove all the shell bearings one at a time, inspect them closely. It's possible you may have damaged one very slightly and that's why it's grabbing the crank.

I don't think the crank is bent, never heard of one ever.

Which journal is the iffy one?
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Online alexdecker

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Re: Crank not rotating
« Reply #22 on: May 07, 2022, 02:21:10 PM »
Ok, so gave it another go on the experimental part, and started moving bearings around a little more aggressively. I found it that not even did the problem follow a specific bearing, but it all came down the the specific screw on the specific bearing being tightened, and then the thing seized up (see picture).

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So I closely inspected it, and lo and behold, didn't even have to inspect it that closely. This is obviously a case of not being able to see the forest for the trees, but this bearing has a spot on it. Now, it's very small, and I can HARDLY see any bulge in the metal with my naked eye - but there is a tiny slight one. It seems much larger in the picture, but trust me, there is almost nothing. Basically nothing. It seems weird to me that such a minuscule spot can seize the entire crankshaft like that. But the problem followed wherever I put that bearing, and that is the only fault I can find in the bearings, so can't think it can be anything else.

What do you guys think?

Also - I can see the colours off most of the bearings, and they are green, brown or black. The offending bearing is green. What would be the best way to go about this issue? Plastigauge all of it, or just buy a new green bearing? Also, I find it really weird that it didn't lock the engine up before taking it apart. All bolts were pretty tight when taking it apart, so it was obviously torqued down alright. Wonder what that is about.

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« Last Edit: May 07, 2022, 02:29:25 PM by alexdecker »

Offline Laverda Dave

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Re: Crank not rotating
« Reply #23 on: May 07, 2022, 02:38:49 PM »
Good that you have found the potential problem.  That shell is toast, no way would I try to use it again, you are talking microns of clearance on these bearings so not worth the potential problems of trying to rescue it.
If it were mine I would plastigauge all the bearings so at least you know what you have got to start with and especially now you have been swapping them around. I would use that as a starting point and buy new bearings to suit.
I still can't see how the bolt caused the bearing to spot in the way it has though, did you inspect every bearing shell during the engine strip and was the spot there before? To my eye it appears as though there was something on the crank journel when you initially torqued the cases and this caused the bearing damage and prevented the crank from turning. I would inspect the case very carefully in case there is a bit of grit floating around in there, same with the crank, give them both a good clean. A piece of grit may have become dislodged when you were hammering the rotor to remove it?
At least you have a way forward now and not a bent crank!
And best to check the crank journel of the damaged bearing for a score mark in the same location as the bearing spot.
« Last Edit: May 07, 2022, 02:41:03 PM by Laverda Dave »
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Offline Oddjob

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Re: Crank not rotating
« Reply #24 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.
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Offline murdock

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Re: Crank not rotating
« Reply #25 on: May 07, 2022, 03:03:25 PM »
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 .


Offline McCabe-Thiele (Ted)

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Re: Crank not rotating
« Reply #26 on: May 07, 2022, 03:11:14 PM »
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.
« Last Edit: May 07, 2022, 03:50:27 PM by McCabe-Thiele (Ted) »
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Online alexdecker

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Re: Crank not rotating
« Reply #27 on: May 07, 2022, 03:34:54 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.

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.

Offline Oddjob

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Re: Crank not rotating
« Reply #28 on: May 07, 2022, 05:57:13 PM »
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?
« Last Edit: May 07, 2022, 05:59:29 PM by Oddjob »
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Online Bryanj

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Re: Crank not rotating
« Reply #29 on: May 07, 2022, 06:12:58 PM »
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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